Contenu connexe Similaire à Bgp 1232073634451868-3 (20) Bgp 1232073634451868-32. Summary
BGP Concept
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 2
3. Summary
BGP Concept
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 3
4. Concepts
The BGP protocol was developed by the IDR Working Group
of IETF. A first version of BGP was published in June 1989
as RFC 1105 (BGP-1). A second version was published in
June 1990 as RFC 1163 (BGP-2). A third version was
published in October 1991 as RFC 1267 (BGP-3).
A fourth version was published in July 1994 as RFC 1654
(BGP-4). The Current version of BGP-4 is documented in
RFC 1771 (March 1995).
BGP-4 supports
the path vector concept to avoid the potential routing loop introduced by
complicated (I.e., full-meshed) Internet topology
IP prefix and length advertisements
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 4
5. BGP Protocol Overview
JUNOS software supports BGP Version 4 and several extensions to
the protocol
RFC 1771, A Border Gateway Protocol 4 (BGP-4)
RFC 1772, Application of the Border Gateway Protocol in the Internet
RFC 1965, Autonomous System Confederations for BGP
RFC 1966, BGP Route Reflection: An Alternative to Full-Mesh IBGP
RFC 1997, BGP Communities Attribute
RFC 2270, Using a Dedicated AS for Sites Homed to a Single Provider
RFC 2283, Multiprotocol Extensions for BGP-4
RFC 2385, Protection of BGP Sessions via the TCP MD5 Signature
Option
RFC 2439, BGP Route Flap Damping
Capabilities Negotiation with BGP4, IETF draft draft-ietf-idr-cap-neg-01
BGP Extended Communities Attribute, IETF draft-ramachandra-bgp-
ext-communities-04.txt
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 5
6. Concepts
the concept of classless interdomain routing to allow better use of
existing IP address space and to minimize the rapid growth of
routing table size (CIDR, RFC 1519)
policy-based routing using a set of pre-defined path attributes
BGP-4 supports route aggregation and AS aggregation (I.e., AS
Set and Confederation)
fast convergence by requiring the router to inform its neighbors
when the previously announced routes become unreachable
large routing table size
authentication using BGP identifier and AS number. In addition, it
supports encrypted signature in every BGP message.
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 6
7. Concepts
BGP routers only use those routes whose next-hop can be reached
BGP routers advertise only those routes that they use
BGP runs over a reliable transport protocol.
TCP port 179
takes care of segmenting, sequencing, retransmission and
acknowledgments
supports a "graceful" close, i.e., that all outstanding data will be
delivered before the connection is close.
- 4096 max frame size
- hold time (90 sec def – smallest used between peers)
- open->updates->keepalives (steady state)-> notification
(close)
| |
------ --- -------
BGP MIB consists of the BGP Peer Table, The BGP Path Attribute
Table and a Global Table.
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 7
8. Concepts
Autonomous System (AS)
The classic definition of an Autonomous System is a set of routers
under a single technical administration, using a single IGP and
common metrics to route packets within the AS, and using an EGP
to route packets to other ASs.
Currently, it has become common for a single AS to use several
IGPs and sometimes several sets of metrics within an AS.
The use of the term Autonomous System here stresses the fact that,
even when multiple IGPs and metrics are used, the administration
of an AS appears to other ASs to have a single coherent interior
routing plan and presents a consistent picture of what
destinations are reachable through it.
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 8
9. Concepts
Autonomous System Type
• Stub AS BGP Peers
Provider "B"
– Single Exit Point
Provider "A"
– Local Traffic Transit AS
AS 60
• Multi-Homed AS Transit AS
– Multiple Exit Points
– Local Traffic AS 50
•Transit AS TCP Connections Customer #1
– Local and Transit Traffic AS 100
Stub As
Stub As
Customer #n
AS 120
Multi-Homed
EBGP Customer #2
IBGP AS 110
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 9
10. BGP AS
What is an AS?
- 16 bit integer (1-65535)
- 64512-65535 private.
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 10
11. Concepts
CIDR = Classless Inter Domain Routing
Address Assignment and Aggregation Strategy
A mechanism to aggregate IP addresses into blocks of
multiple of the old style classes of addresses
Reduces routing information through this aggregation
Conserves Resources
router resources (CPU, memory)
bandwidth (less routes -> less routing packets)
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12. Concepts
Supernet
Organizations are allocated Blocks of IP addresses
These blocks are allocated in powers of 2
The Blocks of Address Space can be Aggregated into one
routing announcement (Supernetting)
Block of 256 “Class C” Networks (or a class B sized block)
IP addresses 192.24.0.0 thru 192.24.255.255
Can be described by one Supernetted Route
192.24.0.0 Mask 255.255.0.0
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13. Concepts
Exterior Routes
Routes learned from other autonomous
systems
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14. Concepts
External Neighbor
Between BGP Speakers in
different AS
Should be directly connected AS 100
Configuration
Router A A
bgp { .1
group EXTERNAL { 1.1.1.0
neighbor 1.1.1.2;
type external; AS 200
peer-as 200 ;
}
{ .2 B
Router B
bgp {
group EXTERNAL {
neighbor 1.1.1.1;
type external;
peer-as 100 ;
}
{
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 14
15. Concepts
Internal Neighbor
Neighbor in same AS
May be several hop away
Configuration
Router A
bgp { AS 100
group INTERNAL {
type internal;
neighbor 1.1.1.1; A
}
}
B
Router B
bgp {
group INTERNAL {
neighbor 2.2.2.2;
type internal;
}
{
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 15
16. Concepts
Internal vs. External BGP
IBGP Update EBGP Update
Local Preference Preserved Removed
MED Preserved Removed the MED from
previous AS
Cluster list Prepend the Cluster ID Unchanged
by RR
Next-hop address Preserved Changed to the local address
AS Path Unchanged Prepend the local AS
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 16
17. BGP Attribute
Well-known mandatory – Always present in a BGP update. All
BGP implementations recognize these attributes. An example
is the BGP next hop attribute. (Origin, AsPath)
Well-known discretionary - Might be present in a BGP update.
All BGP implementations recognize these attributes. An
example is the local preference attribute.
Optional transitive - Must be passed to other BGP peers even if
the local peer does not understand or process the attribute.
An example is the community attribute.
Optional non-transitive - Must not be passed to other BGP
peers. An example is the MED attribute
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 17
18. Concepts
AS path Attributes
Standard attribute types
1, ORIGIN (well-known mandatory)
2, AS_PATH (well-known mandatory)
3, NEXT_HOP (well-known mandatory)
4, MULTI_EXIT_DISC (optional non-transitive)
5, LOCAL_PREF (well-known discretionary)
6, ATOMIC_AGGREGATE (well-known discretionary)
7, AGGREGATOR (optional transitive)
Additional attribute types have been created via supplemental
specifications to extend the protocol
8, Community (optional transitive)
9, Originator Id (optional non-transitive)
10, Cluster list (optional non-transitive)
11, Destination Path Attribute (optional transitive)
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 18
19. Concepts
AS-Path
Path traversed one or more
members of a set
{100 200} (as-set) 100
143.89.14.0/24
206.161.46.0/24
A list of AS’s that a route has 200
206.161.47.0/24
traversed
300 100 (sequence)
300
210.168.35.0/24
143.89.14.0/24 300 100
210.168.35.0/24 300
206.161.46.0/23 300 {100 200}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 19
20. Concepts
Next-hop
set by EBGP speaker or policy
Next hop to reach a network
Router A will advertise 100.100.100.1 next hop for network 150.10.0.0
A AS 109
150.10.0.0/16
100.100.100.0
.1
.2
AS 173
B
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 20
21. Concepts
Next-hop Issue
Router B would advertise 100.100.100.3 as an “next-hop” to reach the
network behind router C to AS 109 ( router A )
Router A
AS 109
.1
EBGP
100.100.100.0/24
.2 .3
AS 173
Router B Router C
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 21
22. Concepts
Next-hop Issue
Problem will occur if the network in-between is actually an NBMA
network !
Router A
AS 109
.1
EBGP
100.100.100.0/24
.2 .3
AS 173
Router B Router C
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 22
23. Concepts
Next-hop Issue
Use “next-hop self” to solve
Router B: Router A
protocol bgp {
AS 109
group BGP-to-router-A {
export chg-nexthop; .1
} EBGP
} 100.100.100.0/24
policy-options policy-statement chg-nexthop {
from protocol bgp; .2 .3
then next-hop self;
AS 173
}
Router B Router C
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 23
24. Concepts
Local Preference
AS 200
AS 666
AS 180
Where to 200 ??
AS 173
Preference send to all routers in local AS
Path with highest preference value are most desirable
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 24
25. Concepts
Local Preference
AS 200
AS 666
AS 180
bgp {
group EXTERNAL { AS 173
type external;
peer-as 666
local-preference 100;
neighbor 1.1.1.1;
}
}
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26. Concepts
Multi-Exit Discriminator (MED)
32-bit, non-negative
Affects all routes from same AS path
Advertised to external neighbors
Lower MED value is more preferable
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 26
27. Concepts
Multi-Exit Discriminator (MED)
AS 666 AS 200
AS 1800
AS 1988
AS 2000
AS 173
Applies on a AS path basis
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 27
28. Concepts
Multi-Exit Discriminator (MED)
Router A:
bgp {
group EXTERNAL {
type external;
neighbor 1.1.1.1 {
export MED; policy-statement MED {
peer-as 666; from as-path via-200;
} then {
} metric 200;
} accept;
}
}
as-path via-200 ".* 200";
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 28
29. Concepts
Multi-Exit Discriminator (MED)
AS 666 set MED = 200 AS 200
A
AS 1800
AS 1988
AS 2000
AS 173
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 29
30. Concepts
Origin
describes how a route was injected into BGP at the originating AS
IGP
Default export type on policy statement for BGP
EGP
From protocol EGP, can be specified in the export policy
Incomplete
Unknown source of information, can be specified in the export
policy
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 30
31. Concepts
Atomic Aggregate
Used to inform BGP speaker about less specific
route.
More specific route exists and is included in it
BGP speaker receiving this attribute shall not
remove the attribute when propagating it
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 31
32. Concepts
Aggregator (6-bytes)
Last AS number that formed the aggregate
route (2 bytes)
IP address of the BGP speaker that formed
the aggregate route (4-bytes)
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33. Concepts
Route Reflector and Confederation
Scaling would be an issue when there are too many BGP
peer within the AS
BGP speaker would not pass the BGP routes learn from
an IBGP peer to another IBGP peers
Number of connection required = n(n-1)/2
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 33
34. Concepts
Route Reflector – RFC 1966
Acting as a “mirror” to reflect the BGP routes learned
from the IBGP peers to the clients
Update from non-client to all clients
Update from client to all non-clients and the other clients
except the one originated the route
Provide the normal BGP speaker function to all other
non-clients
Pending cluster-list and originator ID
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 34
35. Concepts
Route Reflector
IBGP AS300
EBGP EBGP
IBGP
IBGP
IBGP IBGP
AS100 AS200
IBGP
IBGP
IBGP AS300
RR
EBGP EBGP
non-client
IBGP
AS100 AS200
IBGP
client client
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 35
36. Concepts
Route Reflector
Loop Prevention
Originator ID
If the attribute “originator ID” has not been created in the
attribute of the route, the RR will create this attribute
The content of “originator ID” is the router ID of the IBGP peer
that pass this route to the RR
The RR would not reflect the route back to the
originator
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 36
37. Concepts
Route Reflector
Loop Prevention
Cluster list
When the RR reflect the route to other peers, it will prepend it’s
cluster ID within the cluster list
If the RR receive a route with it’s cluster ID within the
cluster list, the route would be discarded
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 37
38. Concepts
Confederation – RFC 1965
Scale down an AS into several Sub-ASs
Each BGP peers between sub-AS would act as EBGP peer
except some of the attributes remain unchanged
Local-preference passed through such a connect
MED, next-hop unchanged between member AS’s of the
confederation.
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 38
39. Concepts
Confederation
IBGP
IBGP
EBGP
IBGP
IBGP
IBGP
IBGP
AS100
IBGP
IBGP IBGP EBGP
AS200 EBGP
AS65500
IBGP
IBGP
IBGP
IBGP
AS100
IBGP
AS65501
AS200
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 39
40. Summary
BGP Concept
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 40
41. BGP Protocol Messages
Four types of messages
Open
Update
Keepalive
Notification
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 41
42. BGP Header
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ +
| Marker |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
•Marker: synchronization and authentication
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43. BGP Open message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
| Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| My Autonomous System |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Hold Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BGP Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opt Parm Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Optional Parameters |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 43
44. OPEN Message (Cont.)
Optional Parameters
Authentication Information (type 1)
0 1 2 3 4 5 6 7 8
+-+-+-+-+-+-+-+-+
| Auth. Code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Authentication Data |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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45. NOTIFICATION Message
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error code | Error subcode | Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 = HRD Error
2 = OPEN Error
3= UPDATE Error
4 = Hold Time Expired
5 = FSM Error
6 = Cease(for fatal errors besides the ones already listed)
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 45
46. UPDATE Message
+-----------------------------------------------------+
| Unfeasible Routes Length (2 octets) |
+-----------------------------------------------------+
| Withdrawn Routes (variable) |
+-----------------------------------------------------+
| Total Path Attribute Length (2 octets) |
+-----------------------------------------------------+
| Path Attributes (variable) |
+-----------------------------------------------------+
| Network Layer Reachability Information (variable) |
+-----------------------------------------------------+
0 1 +---------------------------+
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 | Length (1 octet) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---------------------------+
| Attr. Flags |Attr. Type Code| | Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +---------------------------+
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 46
47. BGP Operation
BGP-4 Message Exchange
BGP Peers
BGP TCP TCP BGP
Idle Idle
Connect Connect
syn Listen
Syn Sent Syn +Ack Syn Received
Established Ack
Initializing Established
Open Open
Initializing
Open Sent Open Sent
Open Confirm KeepAlive KeepAlive Open Confirm
Established Established
Update Update
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 47
48. BGP Operation
BGP-4 FSM
1 Idle
2
3
6
4 Connect
12
5
11
9
13
Open Sent 10
Active
8 7
14
Open Confirm
15
16
Established
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 48
49. BGP Operation
Current New Event
State State
Idle Idle 1). Error
Connect 2). Start
Connect Idle 3). Any other event
Connect 4). ConnectRetry Timer Expired
Open Sent 5). Transport Protocol Connect Succeeds
Active 6). Transport Protocol Connect Fails
Open sent--- Wait for open from peer
Open Sent Idle 7). Stop, Open Error, Connection Collision,
Hold Timer Expires, or any other event
Open Confirm 8). No Errors
Active 9). Disconnect Notification
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 49
50. BGP Operation
Current New Event
State State
Active Open Sent 10). Transport Connect Protocol Succeeds
Connect 11). ConnectRetry Timer Expired
Active 12). Remote Peer Trying, IP Address Not
Expected
Idle 13). Any Other Event
Open Confirm (waiting notification or keepalive – handshake)
Open Confirm Idle 14). Hold Timer Expired, Notification,
Disconnect, Stop, or any other event
Established 15). Keepalive
Established Idle 16). Notification, UPDATE Message error
Disconnect Notification, Hold Timer
Expired, Stop, or any other event
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 50
51. Summary
BGP Concept
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 51
52. Route Control
Route Selection
Route with lowest preference value
Route with highest local preference
Route with the shortest AS path length
Route with the lowest origin code ( IGP < EGP < incomplete )
Route with the lowest MED (cisco-nondeterministic / always-compare-med )
Routes are local generated
Routes from EBGP peer
Routes with the closest next-hop (determined by IGP metric)
Routes from the peer with lowest router-id
Routes from the neighbor with lowest IP address
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 52
53. Route Control
Policy Control
Import / Export Policy
Communities
AS path
Route filtering
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 53
54. Route Control
Import / Export Policy
Per group / neighbor import / export policy
Used for advertise routes originated from the
local AS
Used for change / add / delete BGP attributes
Global specific > Group specific > Neighbor
specific
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 54
55. Route Control
Import / Export Policy
Applying policies:
bgp {
import global-import-policy-here;
export global-export-policy-here;
group testing-policy {
import group-import-policy-here;
export group-export-policy-here;
neighbor 1.1.1.1 {
import neighbor-import-policy-here;
export neighbor-export-policy-here;
}
}
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 55
56. Route Control
Import / Export Policy
Check the routes received from a peer before
applying an import policy:
show route receive-protocol bgp 1.1.1.1
Check the routes sent to a peer after
applying an export policy:
show route advertising-protocol bgp 1.1.1.1
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 56
57. Route Control
Community
Well-known community
no-advertise Do not advertise to neighbors
no-export Do not advertise outside your confederation/AS
no-export-subconfed Do not advertise outside your subconfederation
Define Community
community community-name members [ 100:10 100:30 ];
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 57
58. Route Control
AS Path
AS Path Regular Expressions
{m,n} at least m and most n repetitions of term.
{m} Exact m repetitions of term
{m,} m or more repetitions of term
* Zero or more repetitions of term
+ One or more repetitions of term
? Zero or one repetitions of term
| One of the two terms on either side of the pipe
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 58
59. Route Control
Route filtering
Filteringbased on IP prefix / AS path /
Community string / Neighbor / Origin …..
Import / Export policy
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 59
60. Route Control
Route filtering
Matching criteria
+ as-path Name of AS path regular expression (BGP only)
+ community BGP community
local-preference Local preference associated with a route
+ neighbor Neighboring router
Origin BGP origin attribute
> prefix-list List of prefix-lists of routes to match
> route-filter List of routes to match
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 60
61. Route Control
Route filtering
Matching AS Path
policy-statement filtering {
from as-path testing-as-path;
then accept;
}
as-path testing-as-path ".* 200";
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 61
62. Route Control
Route filtering
Matching Community string
policy-statement filtering {
from community testing-community;
then accept;
}
community testing-community members 100:200;
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63. Route Control
Route filtering
Matching route entry
policy-statement filtering {
from route-filter 100.100.0.0/16 orlonger;
then accept;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 63
64. Route Control
Route filtering
Matching within a group of route entries
prefix-list route-list {
100.100.0.0/16;
100.110.0.0/16;
100.120.0.0/16;
}
policy-statement filtering {
from prefix-list route-list;
then accept;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 64
65. Summary
BGP Concept
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 65
66. Configuration
BGP minimum configuration
[routing-options]
autonomous-system <your own AS>;
[protocol bgp]
group BGP-setup {
type [external | internal];
peer-as <peer’s AS>;
neighbor <peer IP address>;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 66
67. Configuration
Example
[protocol bgp]
group BGP-setup {
type external;
peer-as 100;
neighbor 100.1.1.2;
}
[routing-options]
autonomous-system 200;
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 67
68. Configuration
Set the local-preference
[protocol bgp]
group BGP-setup {
type external;
local-preference 100;
peer-as 100;
neighbor 100.1.1.2;
}
Set the MED
[protocol bgp]
group BGP-setup {
type external;
metric-out 200;
local-preference 100;
peer-as 100;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 68
69. Configuration
Change the origin
[protocol policy-options]
policy-statement change-origin {
from protocol aggregate;
then {
origin incomplete;
accept;
}
}
[protocol bgp]
group BGP-setup {
type external;
export change-origin;
peer-as 100;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 69
70. Configuration
AS-prepend
[policy-options]
policy-statement as-prepend {
from protocol aggregate;
then {
as-path-prepend “300 300 300";
accept;
}
}
[protocol bgp]
group BGP-setup {
type external;
export as-prepend;
peer-as 100;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 70
71. Configuration
Attach community
[protocol bgp]
group BGP-setup {
type external;
export att-community;
peer-as 100;
neighbor 100.1.1.2;
}
[policy-options]
policy-statement att-community {
then {
community set send-community;
}
}
community send-community members [ 100:10 200:10 ];
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 71
72. Configuration
Route Reflector
[protocol bgp]
group RR-client {
type internal;
cluster 100.1.1.1;
neighbor 100.1.1.2;
neighbor 100.1.1.3;
}
group non-client {
type internal;
neighbor 10.1.1.2;
}
group EBGP {
type external;
peer-as 100;
neighbor 192.168.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 72
73. Configuration
Confederation
[routing-options]
autonomous-system 65000;
confederation 200 members [ 65000 65001 ];
[protocol bgp]
group confe {
type external;
peer-as 65001;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 73
74. Configuration
Advertise summary network
[routing-options]
aggregate {
route 202.168.0.0/17 discard;
}
[policy-options]
policy-statement adv-summary {
from protocol aggregate;
then accept;
}
[protocol bgp]
group BGP-setup {
type external;
export adv-summary;
peer-as 100;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 74
75. Configuration
Advertise the routing entries in other protocol
[policy-options]
policy-statement adv-ospf {
from protocol ospf;
then accept;
}
[protocol bgp]
group BGP-setup {
type external;
export adv-ospf;
peer-as 100;
neighbor 100.1.1.2;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 75
76. Summary
BGP concepts
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 76
77. Trouble-shooting
Checking the BGP neighbor status
root@router> show bgp summary
Groups: 1 Peers: 1 Down Peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Damped...
100.1.1.2 65001 275 279 0 0 02:17:30 0/0/0 0/0/0
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 77
78. Trouble-shooting
Neighbor can’t establish
Groups: 1 Peers: 1 Down Peers: 1
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|#Active/Received/Damped...
100.1.1.2 65001 0 4 0 0 00:00:57 Active
Enable traceoption
[protocol bgp]
traceoptions {
file bgp-trace;
flag packets detail;
flag open detail;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 78
79. Trouble-shooting
Monitoring
root@router> monitor start bgp-trace
*** bgp-trace ***
Nov 10 14:53:50
Nov 10 14:53:50 BGP RECV 100.1.1.2+1113 -> 100.1.1.1+179
Nov 10 14:53:50 BGP RECV message type 1 (Open) length 45
Nov 10 14:53:50 BGP RECV version 4 as 65001 holdtime 90 id 192.168.1.2 parmlen 16
Nov 10 14:53:50 MP capability AFI=1, SAFI=1
Nov 10 14:53:50 Refresh capability, code=128
Nov 10 14:53:50 Refresh capability, code=2
Nov 10 14:53:50 bgp_pp_recv: dropping 100.1.1.2 (External AS 65001), connection collision prefers
100.1.1.2+1113 (proto)
Nov 10 14:53:50 bgp_send: sending 45 bytes to 100.1.1.2 (External AS 65001)
Nov 10 14:53:50
Nov 10 14:53:50 BGP SEND 100.1.1.1+179 -> 100.1.1.2+1113
Nov 10 14:53:50 BGP SEND message type 1 (Open) length 45
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 79
80. Trouble-shooting
Monitoring
Nov 10 14:53:50 BGP SEND version 4 as 65000 holdtime 90 id 192.168.1.1 parmlen 16
Nov 10 14:53:50 MP capability AFI=1, SAFI=1
Nov 10 14:53:50 Refresh capability, code=128
Nov 10 14:53:50 Refresh capability, code=2
Nov 10 14:53:50 bgp_send: sending 19 bytes to 100.1.1.2 (External AS 65001)
Nov 10 14:53:50
Nov 10 14:53:50 BGP SEND 100.1.1.1+179 -> 100.1.1.2+1113
Nov 10 14:53:50 BGP SEND message type 4 (KeepAlive) length 19
Nov 10 14:53:50
Nov 10 14:53:50 BGP RECV 100.1.1.2+1113 -> 100.1.1.1+179
Nov 10 14:53:50 BGP RECV message type 3 (Notification) length 21
Nov 10 14:53:50 BGP RECV Notification code 2 (Open Message Error) subcode 2 (bad peer AS
number)
root@router> monitor stop bgp-trace
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 80
81. Trouble-shooting
Configuration
Near end
[routing-options]
autonomous-system 65000;
confederation 200 members [ 65000 65001 65002 ];
[protocol bgp]
group bgp-demo { Far End
type external; [routing-options]
peer-as 65001; autonomous-system 65001;
neighbor 100.1.1.2; confederation 200 members [ 65000 65001 65002 ];
} [protocol bgp]
admin@Jessie# show protocols bgp
group testing {
type external;
peer-as 65002;
neighbor 100.1.1.1;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 81
82. Trouble-shooting
Logged result:
root@router> file show /var/log/?
Possible completions:
<[Enter]> Execute this command
<filename> Filename to display
/var/log/bgp-trace Size: 2459, Last changed: Nov 7 18:41:08
Stop logging:
root@router# delete protocols bgp traceoptions
root@router# commit
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 82
83. Trouble-shooting
Other problem
Local-address definition (cisco’s update-source)
[protocol bgp]
group <group> {
local-address <local IP address>;
}
Peer AS mis-configured
Peer address unreachable
Mulithop issue for EBGP
[protocol bgp]
group <group> {
multihop;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 83
84. Trouble-shooting
Problem Report
“show bgp summary”
“show bgp neighbor”
“show bgp group”
“show version”
“show configuration”
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 84
85. Summary
BGP concepts
BGP Operation
Route Control
Configuration
Trouble-shooting
Juniper vs. Cisco
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 85
86. Presentation and command difference between
Juniper and Cisco
Juniper: Cisco:
fxp1 { interface Loopback0
unit 0 { ip address 192.168.1.254 255.255.255.255
family inet { address 172.27.4.172/24; } !
}
interface Ethernet0
}
ip address 172.27.4.173 255.255.255.0
lo0 {
!
unit 0 {
router bgp 200
family inet { address 192.168.1.3/32; } neighbor 192.168.1.3 remote-as 100
} neighbor 192.168.1.3 ebgp-multihop 255
} neighbor 192.168.1.3 update-source Loopback0
routing-options { !
autonomous-system 100;
}
group Cisco {
type external;
multihop;
Juniper Cisco
local-address 192.168.1.3;
peer-as 200;
neighbor 192.168.1.254;
}
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 86
87. Presentation and command difference between
Juniper and Cisco
root@Juniper> show bgp summary
Groups: 1 Peers: 1 Down Peers: 0
Table Tot Paths Act Paths Suppressed History Damp State Pending
inet.0 0 0 0 0 0 0
inet.2 0 0 0 0 0 0
Peer AS InPkt OutPkt OutQ Flaps Last Up/Dwn State|
#Active/Received/Damped...
192.168.1.254 200 12 14 0 0 00:05:46 0/0/0 0/0/0
Cisco#show ip bgp summary
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
192.168.1.3 4 100 14 14 1 0 0 00:05:39 0
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 87
88. Presentation and command difference between
Juniper and Cisco
root@Juniper> show bgp neighbor
Peer: 192.168.1.254+179 AS 200 Local: 192.168.1.3+3844 AS 100
Type: External State: Established Flags: <>
Last State: OpenConfirm Last Event: RecvKeepAlive
Last Error: None
Options: <Multihop Preference LocalAddress HoldTime PeerAS Refresh>
Local Address: 192.168.1.3 Holdtime: 90 Preference: 170
Number of flaps: 0
Peer ID: 192.168.1.254 Local ID: 192.168.1.3 Active Holdtime: 90
Keepalive Interval: 30
NLRI advertised by peer:
NLRI for this session: inet-unicast
Peer does not support Refresh capability
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 88
89. Presentation and command difference between
Juniper and Cisco
Table inet.0 Bit: 10000
Active Prefixes: 0
Received Prefixes: 0
Suppressed due to damping: 0
Table inet.2 Bit: 20000
Active Prefixes: 0
Received Prefixes: 0
Suppressed due to damping: 0
Last traffic (seconds): Received 3 Sent 3 Checked 3
Input messages: Total 16 Updates 0 Refreshes 0 Octets 304
Output messages: Total 18 Updates 0 Refreshes 0 Octets 368
Output Queue[0]: 0
Output Queue[1]: 0
Route Queue Timer: unset Route Queue: empty
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 89
90. Presentation and command difference between
Juniper and Cisco
Cisco#show ip bgp neighbors
BGP neighbor is 192.168.1.3, remote AS 100, external link
Index 1, Offset 0, Mask 0x2
BGP version 4, remote router ID 192.168.1.3
BGP state = Established, table version = 1, up for 00:08:45
Last read 00:00:15, hold time is 90, keepalive interval is 30 seconds
Minimum time between advertisement runs is 30 seconds
Received 20 messages, 0 notifications, 0 in queue
Sent 20 messages, 0 notifications, 0 in queue
Connections established 1; dropped 0
Last reset never
No. of prefix received 0
External BGP neighbor may be up to 255 hops away.
Connection state is ESTAB, I/O status: 1, unread input bytes: 0
Local host: 192.168.1.254, Local port: 179
Foreign host: 192.168.1.3, Foreign port: 3844
Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 90
91. Presentation and command difference between
Juniper and Cisco
Event Timers (current time is 0x2590F0):
Timer Starts Wakeups Next
Retrans 21 0 0x0
TimeWait 0 0 0x0
AckHold 20 17 0x0
SendWnd 0 0 0x0
KeepAlive 0 0 0x0
GiveUp 0 0 0x0
PmtuAger 0 0 0x0
DeadWait 0 0 0x0
iss: 401687383 snduna: 401687774 sndnxt: 401687774 sndwnd: 16384
irs: 486200570 rcvnxt: 486200977 rcvwnd: 15978 delrcvwnd: 406
SRTT: 342 ms, RTTO: 1337 ms, RTV: 326 ms, KRTT: 0 ms
minRTT: 4 ms, maxRTT: 300 ms, ACK hold: 200 ms
Flags: passive open, nagle, gen tcbs
Datagrams (max data segment is 556 bytes):
Rcvd: 25 (out of order: 0), with data: 20, total data bytes: 406
Sent: 38 (retransmit: 0), with data: 20, total data bytes: 390
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 91
92. Presentation and command difference between
Juniper and Cisco
Juniper Cisco
no synchronization ( Default behavior ) no synchronization
set policy-options damping cisco bgp damping
set routing-options confederation members bgp confederation
set protocols bgp group Cisco cluster bgp cluster-id
show bgp neighbor show ip bgp neighbor
show bgp summary show ip bgp summary
show route aspath-regex "200" show ip bgp regexp ^200$
Updated 8/22/00 Juniper Networks, Inc. Copyright © 2000 - Proprietary & Confidential 92
Notes de l'éditeur Path attributes defined. - Well-known mandatory (recognized and always sent – 010) - Well-known discretionary (recognized not necessarily sent – 010 if sent at all) - Optional transitive (may or may not be recognized, set partial bit if not recognized and pass onwards – 11?) - Optional non-transitive (if not recognized, quietly discard – 100) The local preference attribute is exchanged in IBGP peering sessions only and is not passed to outside AS . The MED represents the external metric of a route - 32 bit, non-negative -- not propagated beyond neighboring AS Because the MED is a nontransitive BGP attribute, the AS that receives a route with an associated MED does not forward the MED value to other ASs . The MED is used in the route selection process only within the AS . . If the route needs to be readvertised to another AS, the MED value must be reset to zero , unless the associated export policy sets an outgoing MED value. If a MED is received over an external BGP link, it is propagated over internal links to other BGP systems within the AS. Whats Origin? - well known mandatory - igp (isis/ospf) - egp (egp) - incomplete (all others – static, rip, etc) - 80% igp in current Internet table. Inform other BGP speaker that the local system choose a less specific route without selecting a more Specific route that is included in it. For example select route 199.1.0.0/16 which include the 199.1.2.0/24 in it To route packet to 192.1.2.9/24 network. Length = 0 - next_hop, MED is unchanged when sent to a neighboring AS in the confederation Local_pref is passed through such a connection Marker: This 16-octet field contains a value that the receiver of the message can predict. If the Type of the message is OPEN, or if the OPEN message carries no Authentication Information (as an Optional Parameter), then the Marker must be all ones. Otherwise, the value of the marker can be predicted by some a computation specified as part of the authentication mechanism (which is specified as part of the Authentication Information) used. The Marker can be used to detect loss of synchronization between a pair of BGP peers, and to authenticate incoming BGP messages. Length: This 2-octet unsigned integer indicates the total length of the message, including the header, in octets. Thus, e.g., it allows one to locate in the transport-level stream the (Marker field of the) next message. The value of the Length field must always be at least 19 and no greater than 4096, and may be further constrained, depending on the message type. No &quot;padding&quot; of extra data after the message is allowed, so the Length field must have the smallest value required given the rest of the message. Type: This 1-octet unsigned integer indicates the type code of the message. The following type codes are defined: 1 - OPEN 2 - UPDATE 3 - NOTIFICATION 4 - KEEPALIVE Version --A 1-byte unsigned integer that indicates the version of the BGP protocol, such as BGP3 or BGP4. During the neighbor negotiation, BGP peers agree on a BGP version number. BGP peers will try to negotiate the highest common version that they both support. Cisco Systems provides the option of predefining the version negotiated to cut down on the negotiation process. Setting the version statically is usually used when the versions of the BGP peers are already known. My Autonomous System --A 2-byte field that indicates the AS number of the BGP router. Hold Time --The maximum amount of time in seconds that may elapse between the receipt of successive KEEPALIVE or UPDATE messages. The hold timer is a counter that increments from zero to the hold time value. Receipt of a KEEPALIVE or UPDATE message causes the hold timer to reset to zero. If the hold time for a particular neighbor is exceeded, the neighbor would be considered dead. The hold time is a 2-byte unsigned integer. The BGP router negotiates with its neighbor to set the hold time at whichever value is lower--its own hold time or its neighbor's. The hold time could be 0, in which case the hold timer and the KEEPALIVE timers are never reset--that is, these timers never expire, and the connection is considered to be always up. If not set to zero, the minimum recommended hold time is three seconds. BGP Identifier --A 4-byte unsigned integer that indicates the sender's ID. In Cisco's implementation, this is usually the router ID (RID), which is calculated as the highest IP address on the router or the highest loopback address at BGP session startup. ( Loopback address is Cisco's representation of the IP address of a virtual software interface that is considered to be up at all times, irrespective of the state of any physical interface.) Optional Parameters --This is a variable length field that indicates a list of optional parameters used in BGP neighbor session negotiation. This field is represented by the triplet <Parameter Type, Parameter Length, Parameter Value> with lengths of 1-byte, 1-byte, and variable length, respectively. An example of optional parameters is the authentication information parameter (type1), which is used to authenticate the session with a BGP peer. Optional Parameter Length --This is a 1-byte unsigned integer that indicates the total length in bytes of the Optional Parameters field. A length value of 0 indicates that no Optional Parameters are present. Unfeasible Routes Length: This 2-octets unsigned integer indicates the total length of the Withdrawn Routes field in octets. Its value must allow the length of the Network Layer Reachability Information field to be determined as specified below. A value of 0 indicates that no routes are being withdrawn from service, and that the WITHDRAWN ROUTES field is not present in this UPDATE message. Withdrawn Routes: This is a variable length field that contains a list of IP address prefixes for the routes that are being withdrawn from service. Each IP address prefix is encoded as a 2-tuple of the form <length, prefix>, whose fields are described below: +---------------------------+ | Length (1 octet) | +---------------------------+ | Prefix (variable) | +---------------------------+ The use and the meaning of these fields are as follows: a) Length: The Length field indicates the length in bits of the IP address prefix. A length of zero indicates a prefix that matches all IP addresses (with prefix, itself, of zero octets). b) Prefix: The Prefix field contains IP address prefixes followed by enough trailing bits to make the end of the field fall on an octet boundary. Note that the value of trailing bits is irrelevant. Total Path Attribute Length: This 2-octet unsigned integer indicates the total length of the Path Attributes field in octets. Its value must allow the length of the Network Layer Reachability field to be determined as specified below. A value of 0 indicates that no Network Layer Reachability Information field is present in this UPDATE message. Path Attributes: A variable length sequence of path attributes is present in every UPDATE. Each path attribute is a triple <attribute type, attribute length, attribute value> of variable length. Attribute Type is a two-octet field that consists of the Attribute Flags octet followed by the Attribute Type Code octet. 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attr. Flags |Attr. Type Code| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ FSM states. - idle (will refuse incoming connection attempts) - connect (listening) - active (trying to establish connection) - opensent (waiting for open from peer) - openconfirm (waiting notification or keepalive – handshake) - established (steady state) . The MED represents the external metric of a route Each routing table is identified by a name, which consists of the protocol family followed by a period and small, nonnegative integer. The protocol family can be inet (Internet), iso (ISO), or mpls (MPLS).The following names are reserved for the default routing tables maintained by the JUNOS software: inet.0 --Default unicast routing table instance-name. inet.0 --Unicast routing table for a particular routing instance inet.1 --Multicast forwarding cache inet.3 --MPLS routing table for path information mpls.0 --MPLS routing table for label-switched path (LSP) next hops If Multiprotocol Border Gateway Protocol (MBGP) is enabled, inet.2 is used for subaddress family indicator (SAFI) 2 routes