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Re: operational reasons to disable IPv6 link-level on some interfaces



Michael Richardson <mcr%sandelman.ca@localhost> writes:

> I have dual connections to two switches, and I have vlan tags:
>
> vr0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:40:63:e2:0b:04
>         media: Ethernet autoselect (100baseTX full-duplex)
>         status: active
> vr1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         address: 00:40:63:e2:0a:8c
>         media: Ethernet autoselect (100baseTX full-duplex)
>         status: active
>
> agr0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>         agrport: vr0, flags=0x3<COLLECTING,DISTRIBUTING>
>         agrport: vr1, flags=0x3<COLLECTING,DISTRIBUTING>
>         address: 00:40:63:e2:0b:04
>         inet 123.123.99.123 netmask 0xffffffc0 broadcast 123.123.11.123
>         inet6 fe80::240:63ff:fee2:b04%agr0 prefixlen 64 scopeid 0x5
>
> vlan82: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1496
>         vlan: 82 parent: agr0
>         address: 00:40:63:e2:0b:04
>         inet 11.222.33.444 netmask 0xffffffe0 broadcast 11.222.33.255
>         inet6 fe80::240:63ff:fee2:b04%vlan82 prefixlen 64 scopeid 0x6
>         inet6 2001:abc:efg:82::251 prefixlen 64
>
> When I look at the network, I see:
>
> rtr3-[~] root 6 #tcpdump -v -e -i agr0 -n -p 
>   (btw: without -p, the NetBSD-5.1-rc2 sometimes crashed)
>
> 15:37:02.715610 00:40:63:e2:0b:04 > 33:33:ff:00:02:54, ethertype 802.1Q 
> (0x8100), length 90: vlan 82, p 0, ethertype IPv6, (hlim 255, next-header: 
> ICMPv6 (58), length: 32) 2001:abc:efg:82::251 > ff02::1:ff00:254: [icmp6 sum 
> ok] ICMP6, neighbor solicitation, length 32, who has 2001:abc:efg:82::254
>           source link-address option (1), length 8 (1): 00:40:63:e2:0b:04
>
> 15:37:02.715925 00:24:38:ef:20:81 > 00:40:63:e2:0b:04, ethertype IPv6 
> (0x86dd), length 86: (class 0xc0, hlim 255, next-header: ICMPv6 (58), length: 
> 32) 2001:abc:efg:82::254 > 2001:abc:efg:82::251: [icmp6 sum ok] ICMP6, 
> neighbor advertisement, length 32, tgt is 2001:abc:efg:82::254, Flags 
> [router, solicited, override]
>           destination link-address option (2), length 8 (1): 00:24:38:ef:20:81

So if that ifconfig -a and trace is from your box, then your machine
sent a neighbor solicited on vlan82, and the ::254 machine sent you a
reply on the bare ethernet - which seems wrong.  I see no evidence that
::251 has misbehaved.  Is ::254 your machine, and does it run NetBSD?

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