pfSense

Forum post here https://forum.pfsense.org/index.php?topic=136009.0

When pfsense receives a packet with a TTL of 1, it should respond with a ICMPv6 Type 3 packet with a source IP of the interface the packet came in on. It has always done this prior to 2.4 and every other router i have seen does this.

I.e. If it received the packet on an interface with an IP of fdda:535f:111b:114c::1 the source IP in the ICMPv6 Type 3 packet should be fdda:535f:111b:114c::1.

But what it is doing is if a packet comes in with a TTL = 1 it is sending a ICMPv6 Type 3 packet with the source IP of the interface that the packet would have been routed out had the TTL been more than 1, i.e. its sending the ICMP packet with a source IP of fdda:535f:111b:2000::1 (WAN)

For the example
LAN = fdda:535f:111b:114c::1
WAN = fdda:535f:111b:2000::1

This can be seen clearly in these traces.

From Lan system to Internet

Tracing route to google.com [2607:f8b0:4006:819::200e]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  2001:470:7:yyy::2 <-pfsense "WAN" IP
  2    29 ms    26 ms    28 ms  2001:470:7:yyy::1
  3    21 ms    23 ms    21 ms  2001:470:0:90::1

what it should look like

Tracing route to google.com [2607:f8b0:4006:819::200e]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  2001:470:xxxx:1::3 <-pfsense "LAN" IP
  2    29 ms    26 ms    28 ms  2001:470:7:yyy::1
  3    21 ms    23 ms    21 ms  ge5-4.core1.ash1.he.net [2001:470:0:90::1]

From Looking Glass to LAN system

racing the route to IPv6 node 2001:470:xxxx:1:7dc5:db6f:aaf8:f195 from 1 to 30 hops

  1    18 ms   18 ms    6 ms 2001:470:0:90::2
  2    23 ms   20 ms   25 ms 2001:470:xxxx:1::3 <-pfsense "LAN" IP
  3    24 ms   25 ms   74 ms 2001:470:xxxx:1:7dc5:db6f:aaf8:f195

what it should look like

Tracing the route to IPv6 node 2001:470:xxxx:1:7dc5:db6f:aaf8:f195 from 1 to 30 hops

  1    18 ms   18 ms    6 ms 2001:470:0:90::2
  2    23 ms   20 ms   25 ms 2001:470:7:yyy::2 <-pfsense "WAN" Ipv6
  3    24 ms   25 ms   74 ms 2001:470:xxxx:1:7dc5:db6f:aaf8:f195