Configuration Note BGP 3107 @ Layer 2: Inter-AS model C Last
Updated: 2014-June-02 Version
1.0
Introduction:
Starting from 6.1R2, the 7705 SAR supports advertising BGP labels across different AS. This document will cover the configurations of BGP 3107 with Inter-AS model C for Layer 2 services.
Setup:
Figure1: BGP 3107 @ Layer 2 setup
Prerequisites
OSPF is used as an IGP protocol in AS 100 and 200; RSVP-TE is used in AS 100 and 200 as the transport tunnel.
Configurations at CE1:
The CE routers have no knowledge of the routes of any other routers in the above topology. A SAP-to-SAP Epipe service has been configured at CE1 to pass the traffic to a remote CE2 router.
A:SAR-13>config>service# info
----------------------------------------------
customer 1 create
description "Default customer"
exit
epipe 50 customer 1 create
sap 1/1/2 create
exit
sap 1/1/3:10 create
exit
no shutdown
exit
-----------------------------------------------
Configurations at PE1:
The PE router has no knowledge of the routes of the CE routers in the above topology. A SAP-to-SDP Epipe service has been configured between PE1 and PE2 respectively. It works as a tunnel to pass the traffic between CE routers.
From 6.1R2 onwards, the 7705 SAR supports “bgp-tunnel” as a new type of MPLS transport tunnel. It is used by SDPs to cross different AS.
A:SAR-69>config>service# info
----------------------------------------------
customer 1 create
description "Default customer"
exit
sdp 1 create
far-end 10.0.0.66
bgp-tunnel
keep-alive
shutdown
exit
no shutdown
exit
epipe 17 customer 1 create
sap 1/2/3:10 create
exit
spoke-sdp 1:17 create
exit
no shutdown
exit
----------------------------------------------
Router PE1 peers with router ASBR1 as an iBGP neighbor. By default, BGP uses LDP as the MPLS transport tunnel. In this lab setup, RSVP-TE has been used as the transport tunnel; hence “transport-tunnel rsvp-te” needs to be configured in the BGP. Or, from 6.1R2, a new CLI command “transport-tunnel mpls” is supported by the 7705 SAR, which will automatically select either RSVP-TE or LDP as the transport tunnel. The “advertise-label ipv4” command will enable the BGP 3107 function to carry label information in BGP update messages.
A:SAR-69>config>router>bgp# info
----------------------------------------------
transport-tunnel rsvp-te
group "local-as"
family ipv4 vpn-ipv4
peer-as 100
neighbor 10.0.0.62
advertise-label ipv4
exit
exit
no shutdown
----------------------------------------------
Configurations at ASBR1:
A routing policy has been configured and applied at the eBGP neighbor to export the /32 address to the far-end ASBR router.
A:SAR-62>config>router>policy-options# info
----------------------------------------------
prefix-list "/32address"
prefix 10.0.0.0/24 longer
exit
policy-statement "/32address-tobgp"
entry 10
from
prefix-list "/32address"
exit
to
protocol bgp
exit
action accept
exit
exit
exit
----------------------------------------------
A:SAR-62>config>router>bgp# info
----------------------------------------------
transport-tunnel rsvp-te
group "local-as"
family ipv4 vpn-ipv4
neighbor 10.0.0.69
peer-as 100
advertise-label ipv4
exit
exit
group "remote-as"
family ipv4
peer-as 200
neighbor 10.62.64.2
export "/32address-tobgp"
advertise-label ipv4
exit
exit
no shutdown
----------------------------------------------
Verify the routes and labels
As shown in the topology below, we will check the labels at each router along the data path from PE1 to PE2.
Figure 2 – Labels cross different routers
Routes and Labels at PE1:
The system IP of routers ASBR2 and PE2 (located in a remote AS) have been learned by router PE1 through BGP.
A:SAR-69# show router route-table
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
10.0.0.62/32 Remote OSPF 10d22h33m 10
10.62.69.1 1000
10.0.0.64/32 Remote BGP 00h59m45s 170
10.0.0.62 (tunneled) 0
10.0.0.66/32 Remote BGP 00h59m45s 170
10.0.0.62 (tunneled) 0
10.0.0.69/32 Local Local 14d04h16m 0
system 0
10.62.69.0/30 Local Local 14d04h08m 0
to-62 0
-------------------------------------------------------------------------------
No. of Routes: 5
Flags: B = BGP backup route available
n = Number of times nexthop is repeated
===============================================================================
The “show router ldp bindings” command shows the TLDP label 131068, which has been pushed at router PE1 to reach router PE2 in the remote AS.
A:SAR-69# show router ldp bindings
===============================================================================
LDP LSR ID: 10.0.0.69
===============================================================================
Legend: U - Label In Use, N - Label Not In Use, W - Label Withdrawn
S - Status Signaled Up, D - Status Signaled Down
E - Epipe Service, V - VPLS Service, M - Mirror Service
A - Apipe Service, F - Fpipe Service, I - IES Service, R - VPRN service
P - Ipipe Service, WP - Label Withdraw Pending, C - Cpipe Service
TLV - (Type, Length: Value), H - Hpipe Service
===============================================================================
LDP Prefix Bindings
===============================================================================
Prefix Peer IngLbl EgrLbl EgrIntf/ EgrNextHop
LspId
-------------------------------------------------------------------------------
No Matching Entries Found
===============================================================================
LDP Service FEC 128 Bindings
===============================================================================
Type VCId SvcId SDPId Peer IngLbl EgrLbl LMTU RMTU
-------------------------------------------------------------------------------
E-Eth 17 17 1 10.0.0.66 131069U 131068S 1500 1500
-------------------------------------------------------------------------------
No. of VC Labels: 1
===============================================================================
LDP Service FEC 129 Bindings
===============================================================================
AGI SAII TAII
Type SvcId SDPId Peer IngLbl EgrLbl LMTU RMTU
-------------------------------------------------------------------------------
No Matching Entries Found
================================================================================
The “show router mpls lsp path to62 detail” command shows RSVP label 131070, which has been pushed at router PE1 to reach router ASBR1.
A:SAR-69# show router mpls lsp path to62 detail
===============================================================================
MPLS LSP to62 Path (Detail)
===============================================================================
Legend :
@ - Detour Available # - Detour In Use
b - Bandwidth Protected n - Node Protected
s - Soft Preemption
===============================================================================
-------------------------------------------------------------------------------
LSP to62 Path loose
-------------------------------------------------------------------------------
LSP Name : to62 Path LSP ID : 38916
From : 10.0.0.69 To : 10.0.0.62
Adm State : Up Oper State : Up
Path Name : loose Path Type : Primary
Path Admin : Up Path Oper : Up
OutInterface: 1/2/1 Out Label : 131070
Path Up Time: 10d 22:49:07 Path Dn Time: 0d 00:00:00
Retry Limit : 0 Retry Timer : 30 sec
RetryAttempt: 0 NextRetryIn : 0 sec
SetupPriori*: 7 Hold Priori*: 0
Bandwidth : No Reservation Oper Bw : 0 Mbps
Hop Limit : 255 Class Type : 0
Record Route: Record Record Label: Record
Oper MTU : 1558 Neg MTU : 1558
Adaptive : Enabled Oper Metric : 1000
Include Grps: Exclude Grps:
None None
Path Trans : 5 CSPF Queries: 0
Failure Code: noError Failure Node: n/a
ExplicitHops:
No Hops Specified
Actual Hops :
10.62.69.2(10.0.0.69) Record Label : N/A
-> 10.62.69.1(10.0.0.62) Record Label : 131070
ResigEligib*: False
LastResignal: n/a CSPF Metric : 0
===============================================================================
The “show router bgp routes” command shows the BGP labels associated with specific prefixes that have been pushed at router PE1 to reach routers ASBR2 and PE2 in the remote AS. These BGP labels were advertised by router ASBR1.
A:SAR-69# show router bgp routes
===============================================================================
BGP Router ID:10.0.0.69 AS:100 Local AS:100
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
Origin codes : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop Path-Id Label
As-Path
-------------------------------------------------------------------------------
u*>i 10.0.0.64/32 100 None
10.0.0.62 None 131066
200
u*>i 10.0.0.66/32 100 1000
10.0.0.62 None 131065
200
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
Labels at ASBR1:
When a packet from router PE1 reaches router ASBR1, BGP label 131066 has been swapped by label 131070 to reach prefix 10.0.0.64 (ASBR2). Similarly, BGP label 131065 has been swapped by label 131067 to reach prefix 10.0.0.66 (PE2).
A:SAR-62# show router bgp routes
===============================================================================
BGP Router ID:10.0.0.62 AS:100 Local AS:100
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
Origin codes : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop Path-Id Label
As-Path
-------------------------------------------------------------------------------
i 10.0.0.62/32 None None
10.62.64.2 None 131069
200 100
u*>i 10.0.0.64/32 None None
10.62.64.2 None 131070
200
u*>i 10.0.0.66/32 None 1000
10.62.64.2 None 131067
200
i 10.0.0.69/32 None None
10.62.64.2 None 131068
200 100
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
The “show router bgp inter-as-label” command displays BGP inter-AS label information. It shows BGP labels received and advertised by this router; it also shows BGP labels originated by this router. Only an ASBR can originate BGP labels for routers within the same AS.
From the output below, router ASBR1 originates BGP labels 131068 and 131069 for router PE1 and itself respectively, and advertises them to router ASBR2. ASBR1 receives two BGP labels, 131067 and 131070, from router ASBR2, and advertises two new BGP labels, 131065 and 131066, to router PE1.
A:SAR-62# show router bgp inter-as-label
===============================================================================
BGP Inter-AS labels
===============================================================================
NextHop Received Advertised Label
Label Label Origin
-------------------------------------------------------------------------------
10.0.0.62 0 131069 Edge
10.0.0.69 0 131068 Internal
10.62.64.2 131067 131065 External
10.62.64.2 131070 131066 External
-------------------------------------------------------------------------------
Total Labels allocated: 4
===============================================================================
Labels at ASBR2:
As with router ASBR1, ASBR2 originates BGP labels 131070 and 131067 for router PE2 and itself respectively, and advertises them to ASBR1. Router ASBR2 receives two BGP labels, 131068 and 131069, from ASBR1, and advertises labels 131066 and 131069 to router PE2.
A:SAR-64# show router bgp inter-as-label
===============================================================================
BGP Inter-AS labels
===============================================================================
NextHop Received Advertised Label
Label Label Origin
-------------------------------------------------------------------------------
10.0.0.64 0 131070 Edge
10.0.0.66 0 131067 Internal
10.62.64.1 131068 131066 External
10.62.64.1 131069 131069 External
-------------------------------------------------------------------------------
Total Labels allocated: 4
===============================================================================
A:SAR-64# show router bgp routes
===============================================================================
BGP Router ID:10.0.0.64 AS:200 Local AS:200
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
Origin codes : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop Path-Id Label
As-Path
-------------------------------------------------------------------------------
u*>i 10.0.0.62/32 None None
10.62.64.1 None 131069
100
i 10.0.0.64/32 None None
10.62.64.1 None 131067
100 200
i 10.0.0.66/32 None None
10.62.64.1 None 131066
100 200
u*>i 10.0.0.69/32 None 1000
10.62.64.1 None 131068
100
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
A:SAR-64# show router mpls lsp path to66 detail
===============================================================================
MPLS LSP to66 Path (Detail)
===============================================================================
Legend :
@ - Detour Available # - Detour In Use
b - Bandwidth Protected n - Node Protected
s - Soft Preemption
===============================================================================
-------------------------------------------------------------------------------
LSP to66 Path loose
-------------------------------------------------------------------------------
LSP Name : to66 Path LSP ID : 5632
From : 10.0.0.64 To : 10.0.0.66
Adm State : Up Oper State : Up
Path Name : loose Path Type : Primary
Path Admin : Up Path Oper : Up
OutInterface: 1/1/5 Out Label : 131065
Path Up Time: 0d 00:08:54 Path Dn Time: 0d 00:00:00
Retry Limit : 0 Retry Timer : 30 sec
RetryAttempt: 0 NextRetryIn : 0 sec
SetupPriori*: 7 Hold Priori*: 0
Bandwidth : No Reservation Oper Bw : 0 Mbps
Hop Limit : 255 Class Type : 0
Record Route: Record Record Label: Record
Oper MTU : 1558 Neg MTU : 1558
Adaptive : Enabled Oper Metric : 1000
Include Grps: Exclude Grps:
None None
Path Trans : 1 CSPF Queries: 0
Failure Code: noError Failure Node: n/a
ExplicitHops:
No Hops Specified
Actual Hops :
10.66.64.1(10.0.0.64) Record Label : N/A
-> 10.66.64.2(10.0.0.66) Record Label : 131065
ResigEligib*: False
LastResignal: n/a CSPF Metric : 0
===============================================================================
Labels at PE2:
A:SAR-66# show router bgp routes
===============================================================================
BGP Router ID:10.0.0.66 AS:200 Local AS:200
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
Origin codes : i - IGP, e - EGP, ? - incomplete, > - best, b - backup
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop Path-Id Label
As-Path
-------------------------------------------------------------------------------
u*>i 10.0.0.62/32 100 None
10.0.0.64 None 131069
100
u*>i 10.0.0.69/32 100 1000
10.0.0.64 None 131066
100
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
OAM over BGP tunnel
To use lsp-ping and lsp-trace, a transport tunnel (RSVP-TE/LDP) in each AS must be configured. However, a transport tunnel (RSVP-TE/LDP) between two PEs of different AS is not required.
Lsp-ping can be used to verify the status of the BGP tunnel from one AS to another AS.
A:SAR-69# oam lsp-ping bgp-label prefix 10.0.0.66/32
LSP-PING 10.0.0.66/32: 80 bytes MPLS payload
Seq=1, send from intf to-62, reply from 10.0.0.66
udp-data-len=32 ttl=255 rtt=39.5ms rc=4 (NoFECMapping)
---- LSP 10.0.0.66/32 PING Statistics ----
1 packets sent, 1 packets received, 0.00% packet loss
round-trip min = 39.5ms, avg = 39.5ms, max = 39.5ms, stddev = 0.000ms
Lsp-trace can be used to gather hop information along the path of the BGP tunnel.
A:SAR-69# oam lsp-trace bgp-label prefix 10.0.0.66/32
lsp-trace to 10.0.0.66/32: 0 hops min, 0 hops max, 104 byte packets
1 10.0.0.62 rtt=3.43ms rc=8(DSRtrMatchLabel)
2 10.0.0.64 rtt=3.49ms rc=8(DSRtrMatchLabel)
3 10.0.0.66 rtt=1.20ms rc=4(NoFECMapping