Operation on a BGP IPv4 LSP resolved over an SR-ISIS IPv4 tunnel or an SR-OSPF IPv4 tunnel

The 7210 SAS enhances lsp-ping and lsp-trace of a BGP IPv4 LSP resolved over an SR-ISIS IPv4 tunnel or an SR-OSPF IPv4 tunnel. The 7210 SAS enhancement reports the full set of ECMP next-hops for the transport tunnel at both ingress PE and at the ABR or ASBR. The list of downstream next-hops is reported in the DSMAP or DDMAP TLV.

If an lsp-trace of the BGP IPv4 LSP is initiated with the path-destination option specified, the CPM hash code at the responder node selects the outgoing interface to return in the DSMAP or DDMAP TLV. The decision is based on the modulo operation of the hash value on the label stack or the IP headers (where the DST IP is replaced by the specific 127/8 prefix address in the multipath type 8 field of the DSMAP or DDMAP) of the echo request message and the number of outgoing interfaces in the ECMP set.

The following figure shows a sample topology used in the subsequent BGP over SR-OSPF and BGP over SR-ISIS examples.

Figure: Sample topology for BGP over SR-OSPF and SR-ISIS

The following outputs are examples of the lsp-trace command for a hierarchical tunnel consisting of a BGP IPv4 LSP resolved over an SR-ISIS IPv4 tunnel or an SR-OSPF IPv4 tunnel.

Example

The following output is an example of BGP over SR-OSPF.

*A:Dut-A# oam lsp-trace bgp-label prefix 10.21.1.6/32 detail downstream-map-
tlv ddmap path-destination 127.1.1. 
lsp-trace to 10.21.1.6/32: 0 hops min, 0 hops max, 168 byte packets
1  10.20.1.3  rtt=2.31ms rc=8(DSRtrMatchLabel) rsc=2 
     DS 1: ipaddr=10.10.5.5 ifaddr=10.10.5.5 iftype=ipv4Numbered MRU=1496 
           label[1]=27506 protocol=5(OSPF)
           label[2]=262137 protocol=2(BGP)
     DS 2: ipaddr=10.10.11.4 ifaddr=10.10.11.4 iftype=ipv4Numbered MRU=1496 
           label[1]=27406 protocol=5(OSPF)
           label[2]=262137 protocol=2(BGP)
     DS 3: ipaddr=10.10.11.5 ifaddr=10.10.11.5 iftype=ipv4Numbered MRU=1496 
           label[1]=27506 protocol=5(OSPF)
           label[2]=262137 protocol=2(BGP)
2   10.20.1.4  rtt=4.91ms rc=8(DSRtrMatchLabel) rsc=2 
     DS 1: ipaddr=10.10.9.6 ifaddr=10.10.9.6 iftype=ipv4Numbered MRU=1492 
           label[1]=27606 protocol=5(OSPF)
           label[2]=262137 protocol=2(BGP)
3  10.20.1.6  rtt=4.73ms rc=3(EgressRtr) rsc=2 
3  10.20.1.6  rtt=5.44ms rc=3(EgressRtr) rsc=1 
*A:Dut-A#

Example

The following output is an example of BGP over SR-ISIS.

A:Dut-A# oam lsp-trace bgp-label prefix 10.21.1.6/32 detail downstream-map-
tlv ddmap path-destination 127.1.1.1 
lsp-trace to 10.21.1.6/32: 0 hops min, 0 hops max, 168 byte packets
1  10.20.1.3  rtt=3.33ms rc=8(DSRtrMatchLabel) rsc=2 
    DS 1:  ipaddr=10.10.5.5 ifaddr=10.10.5.5 iftype=ipv4Numbered MRU=1496 
           label[1]=28506 protocol=6(ISIS)
           label[2]=262139 protocol=2(BGP)
     DS 2: ipaddr=10.10.11.4 ifaddr=10.10.11.4 iftype=ipv4Numbered MRU=1496 
           label[1]=28406 protocol=6(ISIS)
           label[2]=262139 protocol=2(BGP)
     DS 3: ipaddr=10.10.11.5 ifaddr=10.10.11.5 iftype=ipv4Numbered MRU=1496 
           label[1]=28506 protocol=6(ISIS)
           label[2]=262139 protocol=2(BGP)
2  10.20.1.4  rtt=5.12ms rc=8(DSRtrMatchLabel) rsc=2 
     DS 1: ipaddr=10.10.9.6 ifaddr=10.10.9.6 iftype=ipv4Numbered MRU=1492 
           label[1]=28606 protocol=6(ISIS)
           label[2]=262139 protocol=2(BGP)
3  10.20.1.6  rtt=8.41ms rc=3(EgressRtr) rsc=2 
3  10.20.1.6  rtt=6.93ms rc=3(EgressRtr) rsc=1

Assuming the topology in the following figure includes an eBGP peering between nodes B and C, the BGP IPv4 LSP spans the AS boundary and resolves to an SR-ISIS tunnel within each AS.

Figure: Sample topology for BGP over SR-ISIS in inter-AS option C

Example

The following output is an example of BGP over SR-ISIS using inter-AS option C.

*A:Dut-A# oam lsp-trace bgp-label prefix 10.20.1.6/32 src-ip-
address 10.20.1.1 detail downstream-map-tlv ddmap path-destination 127.1.1.1 
lsp-trace to 10.20.1.6/32: 0 hops min, 0 hops max, 168 byte packets
1  10.20.1.2  rtt=2.69ms rc=3(EgressRtr) rsc=2 
1  10.20.1.2  rtt=3.15ms rc=8(DSRtrMatchLabel) rsc=1 
     DS 1: ipaddr=10.10.3.3 ifaddr=10.10.3.3 iftype=ipv4Numbered MRU=0 
           label[1]=262127 protocol=2(BGP)
2  10.20.1.3  rtt=5.26ms rc=15(LabelSwitchedWithFecChange) rsc=1 
     DS 1: ipaddr=10.10.5.5 ifaddr=10.10.5.5 iftype=ipv4Numbered MRU=1496 
           label[1]=26506 protocol=6(ISIS)
           label[2]=262139 protocol=2(BGP)
           fecchange[1]=PUSH fectype=SR Ipv4 Prefix prefix=10.20.1.6 remotepeer=10.1
0.5.5 
3  10.20.1.5  rtt=7.08ms rc=8(DSRtrMatchLabel) rsc=2 
     DS 1: ipaddr=10.10.10.6 ifaddr=10.10.10.6 iftype=ipv4Numbered MRU=1496 
           label[1]=26606 protocol=6(ISIS)
       label[2]=262139 protocol=2(BGP)
4  10.20.1.6  rtt=9.41ms rc=3(EgressRtr) rsc=2 
4  10.20.1.6  rtt=9.53ms rc=3(EgressRtr) rsc=1