[need help]BGP multihop setup with Bird - some issue about [BGP Error: Hold timer expired]

crazychen

I don't understand Multihop in BGP. I'm having a bit of trouble, the session is established normally, but every 15 seconds (Hold timer interval), the connection is disconnected, the routes in the session are sent and received normally (Established conn), is there something I need to adjust?

MY Endpoint:185.243.218.A / 2a03:94e0:ffff:185:243:218::A / AS12345
UP Endpoint:185.125.170.253 / 2a03:94e0:f253:: / AS56655

root@debian:~# traceroute 185.125.170.253
traceroute to 185.125.170.253 (185.125.170.253), 30 hops max, 60 byte packets
 1  185.243.218.3 (185.243.218.3)  0.205 ms  9.474 ms  9.467 ms
 2  185.125.170.253 (185.125.170.253)  9.460 ms  9.450 ms  9.440 ms
root@debian:~# traceroute 2a03:94e0:f253::
traceroute to 2a03:94e0:f253:: (2a03:94e0:f253::), 30 hops max, 80 byte packets
 1  2a03:94e0:ffff:185:243:218:0:2 (2a03:94e0:ffff:185:243:218:0:2)  0.217 ms  0.245 ms  0.284 ms
 2  2a03:94e0:f253:: (2a03:94e0:f253::)  0.223 ms  0.262 ms  0.250 ms

Minimize Bird Conf:

protocol static {
    ipv4;

    route 185.125.170.253/32 via 185.243.218.3 via 185.243.218.A; 
}

protocol static {
    ipv6;

    route 2a03:94e0:f253::/128 via 2a03:94e0:ffff:185:243:218:0:2 via 2a03:94e0:ffff:185:243:218::A;
}

template bgp bgppeers {
    graceful restart on;
    local as 12345;
    default bgp_local_pref 100; 

    hold time 30;
    keepalive time 1;

    multihop 3;

    ipv4 {
        import filter {
            if ( roa_check(roa4_internet, net, bgp_path.last) = ROA_INVALID ) then reject;
            accept;
        };
        export filter {
            reject;
        };
    };

    ipv6 {
        import filter {
            if ( roa_check(roa6_internet, net, bgp_path.last) = ROA_INVALID ) then reject;
            accept;
        };
        export filter {
            reject;
        };
    };
}

protocol bgp terrahost_v4 from bgppeers {
  source address 185.243.218.A;
  neighbor 185.125.170.253 as 56655;

  ipv6 {
    import none;
    export none;
  };
}

protocol bgp terrahost_v6 from bgppeers {
  source address 2a03:94e0:ffff:185:243:218::A;
  neighbor 2a03:94e0:f253:: as 56655;

  ipv4 {
    import none;
    export none;
  };
}

tomle

Remove the static routes for the remote peer, it breaks your routing.

crazychen

@tomle said:
Remove the static routes for the remote peer, it breaks your routing.

Thank you for your help.

also get [BGP Error: Hold timer expire]

protocol static {
    ipv4;
}

protocol static {
    ipv6;
}

tomle

What's your route -n when connected?

crazychen

@tomle said:
What's your route -n when connected?

root@debian:~# birdc s p 
BIRD 2.0.7 ready.
Name       Proto      Table      State  Since         Info
cloudflare RPKI       ---        up     20:51:45.486  Sync-Running
kernel1    Kernel     master4    up     20:51:45.483  
kernel2    Kernel     master6    up     20:51:45.483  
static1    Static     master4    up     20:51:45.483  
static2    Static     master6    up     20:51:45.483  
terrahost_v4 BGP        ---        up     20:51:50.300  Established   
terrahost_v6 BGP        ---        up     20:51:49.255  Established   
root@debian:~# !ro
route -n | head
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         185.243.218.1   0.0.0.0         UG    0      0        0 vmbr0
41.86.37.0      -               255.255.255.0   !     32     -        0 -
41.209.0.0      -               255.255.192.0   !     32     -        0 -
44.31.85.0      -               255.255.255.0   !     32     -        0 -
45.12.135.0     -               255.255.255.0   !     32     -        0 -
45.173.54.0     -               255.255.255.0   !     32     -        0 -
45.183.178.0    -               255.255.255.0   !     32     -        0 -
103.165.184.0   -               255.255.254.0   !     32     -        0 -

wait ~20s

root@debian:~# birdc s p 
BIRD 2.0.7 ready.
Name       Proto      Table      State  Since         Info
cloudflare RPKI       ---        up     20:51:45.486  Established
kernel1    Kernel     master4    up     20:51:45.483  
kernel2    Kernel     master6    up     20:51:45.483  
static1    Static     master4    up     20:51:45.483  
static2    Static     master6    up     20:51:45.483  
terrahost_v4 BGP        ---        start  20:56:43.705  Idle          BGP Error: Hold timer expired
terrahost_v6 BGP        ---        start  20:55:52.641  Idle          BGP Error: Hold timer expired
root@debian:~# route -n | head
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         185.243.218.1   0.0.0.0         UG    0      0        0 vmbr0
185.243.218.0   0.0.0.0         255.255.255.0   U     0      0        0 vmbr0
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 vmbr1
root@debian:~# 

terrahost

Hey, you should not have to specify hold timer. Please remove that. Since ours will be lower thats what they will agree on when establishing connection.

crazychen

@terrahost said:
Hey, you should not have to specify hold timer. Please remove that. Since ours will be lower thats what they will agree on when establishing connection.

It will automatically negotiate, in fact, it is useless to delete it.