[j-nsp] wrong IP in traceroutes

[Baldur Norddahl]

Hello

Sometimes we get the wrong IP back in traceroutes. Here is an example:

gigabit at kviknet01:~$ mtr -n -r -c3 185.24.168.181
Start: 2021-05-15T14:58:20+0000
HOST: kviknet01.ring.nlnog.net    Loss%   Snt   Last   Avg  Best  Wrst StDev
  1.|-- 212.237.176.65             0.0%     3    0.2   0.2   0.2   0.2   0.0
  2.|-- 185.107.12.27              0.0%     3    0.5   0.5   0.4   0.5   0.0
  3.|-- 45.145.95.250              0.0%     3    0.3   0.3   0.3   0.3   0.0
  4.|-- 10.10.123.7                0.0%     3   10.1  12.6  10.1  16.5   3.4
(more hops)

Hop #3 should have been 185.24.168.29. Instead we get 45.145.95.250 which
is unfortunate because that address belongs to a customer and it is not
even within the IP ranges allocated to us. The customer owns his own
address space directly with RIPE.

The interface is this:

admin at gc-edge1# show interfaces ps44
description "Kviknet peering BGP";
anchor-point {
    lt-0/0/0;
}
vlan-tagging;
unit 0 {
    encapsulation ethernet-vpls;
}
unit 40 {
    alias kviknet;
    vlan-id 40;
    family inet {
        address 185.24.168.29/30;
    }
    family inet6 {
        address 2a00:7660:100:26::2/126;
    }
}

The IP address from the traceroute is this one:

admin at gc-edge1# show interfaces ps3
anchor-point {
    lt-0/0/0;
}
unit 0 {
    encapsulation ethernet-ccc;
}
unit 1 {
    family inet {
        address 45.145.95.250/29;
    }
    family inet6 {
        address 2a00:7660:100:1::2/125;
    }
}

The traffic did obviously not go via ps3 as that connects directly to a
single homed customer.

Is this a bug? Can I do something to get a better choice for IP address in
traceroutes? It appears to be linked to the fact this goes via a "ps"
interface.

Thanks,

Baldur