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[Edgecore SONiC] BGP Unnumbered Follow

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kojui_chang 張恪睿
  • Updated

In the original BGP configuration, it needs to specify a peer IPv4 address to establish peer connections.

For CLOS deployment in the data center, the IP interfaces grow dramatically due to the full connection between spines and LEAFs.

(each peer connection needs IPv4 addresses on it). To eliminate this situation, we need the unnumbered interface to establish peer connections.

Restriction

  • "BGP unnumbered" support for Layer 3 interfaces that bind IP on a port or port-channel interface.
  • (202006.x, 202012.x) "BGP unnumbered" support VLAN interface, but it must configure IPv4 address to VLAN interface to activate IPv6 link-local IP address, please make sure there's only one Interface added to the VLAN since BGP session is point to point.
    • The reason why VLAN interface needs extra IP address to be configured is IPv6 link-local address is created automatically on Linux netdevice. If user create 4k VLAN, it will create the 4k corresponding router interface even it doesn't configure any IP address. This will exhaust ASIC resources in this scenario, so we limit IPv6 link-local address to create router interface automatically. In order to make BGP unnumbered work, it indeed needs a router interface on it, so we let user to configure extra IP on it as a workaround

Tested model & firmware version:

  • Switch model name:

       AS7362-56X

       AS7726-32X

       AS5835-54X(T)

  • Edgecore SONiC version: 

202006.4

202012.2

Establish BGP unnumbered session

mceclip0.png

Procedure:

Step 1. Initialize FRR configuration. Please refer to FRRouting and config initialization tutorial.

Step 2. Configure IP address properly for BGP session. Please refer to Management and front port IPv4/IPv6 Address tutorial.

Step 3. Enter Vty shell.

admin@sonic:~$ vtysh
Hello, this is FRRouting (version 7.2.1-sonic).
Copyright 1996-2005 Kunihiro Ishiguro, et al.

sonic#

Note.

"vtysh" provides a combined frontend to all FRR daemons in a single combined session.

Step 4. Configuring BGP Neighbor Session with unnumbered. Replaces the IP configuration of the original neighbor with the locally connected interface. (refer to Establish BGP session)

Switch#1's setting.
sonic# configure terminal
sonic(config)# router bgp 65000 
sonic(config-router)#bgp router-id 3.3.3.3 
sonic(config-router)# neighbor Ethernet8 interface remote 65001 

Switch#2's setting.
sonic# configure terminal 
sonic(config)# router bgp 65001 
sonic(config-router)#bgp router-id 4.4.4.4 
sonic(config-router)# neighbor Ethernet48 interface remote 65000

Note.

The AS number of neighbors, you could assign the AS number of neighbors. The "external" is to eBGP and the "internal" is to iBGP. 

eBGP:
sonic(config-router)# neighbor Ethernet8 interface remote-as external
iBGP:
sonic(config-router)# neighbor Ethernet8 interface remote-as internal

 

Step 5. Checking the BGP connection and neighbor status.

On the AS7726-32X (Switch1)

sonic# show bgp summary

IPv4 Unicast Summary:
BGP router identifier 3.3.3.3, local AS number 65000 vrf-id 0
BGP table version 0
RIB entries 0, using 0 bytes of memory
Peers 1, using 20 KiB of memory

Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
Ethernet8       4      65001      13      20        0    0    0 00:00:15            0

Total number of neighbors 1

sonic# show bgp neighbors
BGP neighbor on Ethernet8: 10.3.0.2, remote AS 65001, local AS 65000, external link
Hostname: sonic
  BGP version 4, remote router ID 4.4.4.4, local router ID 3.3.3.3
  BGP state = Established, up for 00:01:02
  Last read 00:00:02, Last write 00:00:02
  Hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: sonic,domain name: n/a) received (name: sonic,domain name: n/a)
    Graceful Restart Capabilty: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  6          5
    Notifications:          8          2
    Updates:                3          3
    Keepalives:             4          4
    Route Refresh:          0          0
    Capability:             0          0
    Total:                 21         14
  Minimum time between advertisement runs is 0 seconds
 For address family: IPv4 Unicast
  Update group 3, subgroup 3
  Packet Queue length 0
  Community attribute sent to this neighbor(all)
  0 accepted prefixes
  Connections established 3; dropped 2
  Last reset 00:01:04,   No AFI/SAFI activated for peer
  Message received that caused BGP to send a NOTIFICATION:
    FFFFFFFF FFFFFFFF FFFFFFFF FFFFFFFF
    004E0104 FDE900B4 04040404 31020601
    04000100 01020280 00020202 00020641
    040000FD E9020645 04000101 01020949
    0705736F 6E696300 02044002 8078
Local host: 10.3.0.3, Local port: 179
Foreign host: 10.3.0.2, Foreign port: 55286
Nexthop: 10.3.0.3
Nexthop global: fe80::3e2c:99ff:fe8b:41bc
Nexthop local: fe80::3e2c:99ff:fe8b:41bc
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 120
Read thread: on  Write thread: on  FD used: 29

On the AS5835-54X  (Switch2)

sonic# show bgp summary

IPv4 Unicast Summary:
BGP router identifier 4.4.4.4, local AS number 65001 vrf-id 0
BGP table version 0
RIB entries 0, using 0 bytes of memory
Peers 1, using 20 KiB of memory

Neighbor        V         AS MsgRcvd MsgSent   TblVer  InQ OutQ  Up/Down State/PfxRcd
Ethernet48      4      65000      13      14        0    0    0 00:02:31            0

Total number of neighbors 1
sonic# show bgp neighbors
BGP neighbor on Ethernet48: 10.3.0.3, remote AS 65000, local AS 65001, external link
Hostname: sonic
  BGP version 4, remote router ID 3.3.3.3, local router ID 4.4.4.4
  BGP state = Established, up for 00:02:35
  Last read 00:00:35, Last write 00:00:35
  Hold time is 180, keepalive interval is 60 seconds
  Neighbor capabilities:
    4 Byte AS: advertised and received
    AddPath:
      IPv4 Unicast: RX advertised IPv4 Unicast and received
    Route refresh: advertised and received(old & new)
    Address Family IPv4 Unicast: advertised and received
    Hostname Capability: advertised (name: sonic,domain name: n/a) received (name: sonic,domain name: n/a)
    Graceful Restart Capabilty: advertised and received
      Remote Restart timer is 120 seconds
      Address families by peer:
        none
  Graceful restart information:
    End-of-RIB send: IPv4 Unicast
    End-of-RIB received: IPv4 Unicast
  Message statistics:
    Inq depth is 0
    Outq depth is 0
                         Sent       Rcvd
    Opens:                  4          3
    Notifications:          2          2
    Updates:                3          3
    Keepalives:             5          5
    Route Refresh:          0          0
    Capability:             0          0
    Total:                 14         13
  Minimum time between advertisement runs is 0 seconds


 For address family: IPv4 Unicast
  Update group 3, subgroup 3
  Packet Queue length 0
  Community attribute sent to this neighbor(all)
  0 accepted prefixes

  Connections established 3; dropped 2
  Last reset 00:02:37,   Notification sent (Cease/Other Configuration Change)
Local host: 10.3.0.2, Local port: 55286
Foreign host: 10.3.0.3, Foreign port: 179
Nexthop: 10.3.0.2
Nexthop global: fe80::6f8:f8ff:fe8d:81e1
Nexthop local: fe80::6f8:f8ff:fe8d:81e1
BGP connection: shared network
BGP Connect Retry Timer in Seconds: 120
Read thread: on  Write thread: on  FD used: 28

 Step 6. Save the routing setting.

sonic# write

Note: this version of vtysh never writes vtysh.conf
Building Configuration...
Integrated configuration saved to /etc/frr/frr.conf
[OK]

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