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Cisco Bug: CSCvu57398 - IPV6 Multihop BFD does not comes up between N9K and non-N9K device under ebgp setup

Last Modified

Oct 06, 2020

Products (1)

  • Cisco Nexus 9000 Series Switches

Known Affected Releases


Description (partial)

If we are using Multi-hop BFD between N9K and Non-N9K device with update-source loopback on N9K and SVI on Non-N9K. N9K and  Non-N9K are in different AS with ebgp neighborship inbetween. The  BFD view on N9K is multi-hop but on non-N9K is single-hop. It means the device across the link will send BFD message with  port number of the single hop. 

In 'show bfd ipv6 neighbor', we can see the following output even we have ebgp-multihop 255 configured

OurAddr NeighAddr
LD/RD         RH/RS    Holdown(mult)             State                   Int             Vrf     Type
fa00:1::1   fc00:1::2    1090519045/0    Down    N/A(3) Down Vlan100  default    SH

For connectivity wise,
Direct BGP is up
Multihop BGP is up
Ping6 is passing
BFD got ICMPV6 unreachable 
BFD is at state admin down
TX is sending but RX counter remain 0

Session state is Down and not using echo function

Session type: Singlehop
Rx Count: 0, Rx Interval (ms) min/max/avg: 0/0/0 last: 743090 ms ago
Tx Count: 389, Tx Interval (ms) min/max/avg: 1893/1893/1893 last: 1479 ms ago
State bit: AdminDown - Demand bit: 0
Min Echo interval: 0 - Authentication bit: 0
Hosting LC: 1, Down reason: No Diagnostic, Reason not-hosted: None

IPV6 Multi-hop BFD does not comes up between N9K and non-N9K devices under ebgp setup even the full connectivity is maintained.

pesudo configuration
router bgp 1
neighbor <IPV6 addr>
bfd multihop interval 250 min_rx 250 multiplier 3
remote-as 2
update-source loopback0
ebgp-multihop 255
address-family ipv6 unicast

vica versa on ASR

N9K is running 9.3.4 software release
  BIOS: version 05.40
 NXOS: version 9.3(4)

Tested between N9K <-----AS1--------ebgp-------AS2-----> ASR directly connected. N9K side with following
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