IS-IS and IPv6 LLA next-hop - just Arista, or everyone?
athompson at merlin.mb.ca
Tue May 4 15:15:40 UTC 2021
Thank you, both!
...that kinda sucks, though.
I don't see any rationale in RFC 5308 for why the HELLO packet may only contain the LLA - does anyone know/remember why? (I'm hoping that understanding the rationale will make this an easier pill to swallow.) Obviously this behaviour/requirement is net-new to the IPv6 TLVs, as there's no LLA-cognate in IPv4 (APIPA doesn't count). There is in OSI, I think, but I'm still too sane to read those docs.
It makes sense that you would not want LLAs in LSPs, only GUAs, but does that imply that you must use either ULAs or GUAs in order to establish IPv6 routes in IS-IS, in an IPv6 environment? That makes about as much sense to me as forcing LLAs for next-hops.
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athompson at merlin.mb.ca<mailto:athompson at merlin.mb.ca>
From: NANOG <nanog-bounces+athompson=merlin.mb.ca at nanog.org> on behalf of Saku Ytti <saku at ytti.fi>
Sent: May 4, 2021 01:44
To: Mark Tinka <mark at tinka.africa>
Cc: nanog list <nanog at nanog.org>
Subject: Re: IS-IS and IPv6 LLA next-hop - just Arista, or everyone?
On Tue, 4 May 2021 at 07:24, Mark Tinka <mark at tinka.africa> wrote:
>> 2c0f:feb0::1/128 *[IS-IS/18] 02:43:49, metric 5870
> to fe80::1205:caff:fe86:4ac3 via et-4/0/2.0
> to fe80::5287:89ff:fef3:25c3 via et-4/0/2.0
> to fe80::1205:caff:fe86:4b10 via et-5/0/2.0
> > to fe80::5287:89ff:fef3:2610 via et-5/0/2.0
> IOS XE:
> I2 2C0F:FEB0::1/128 [115/6410]
> via FE80::1205:CAFF:FE86:4AC3, TenGigabitEthernet1/0/0
> via FE80::1205:CAFF:FE86:4B10, TenGigabitEthernet0/0/0
> via FE80::5287:89FF:FEF3:25C3, TenGigabitEthernet1/0/0
> via FE80::5287:89FF:FEF3:2610, TenGigabitEthernet0/0/0
> IOS XR:
> i L2 2c0f:feb0::1/128
> [115/5870] via fe80::1205:caff:fe86:4b10, 02:45:22, HundredGigE0/3/0/0 (!)
> [115/5810] via fe80::f60f:1bff:feb0:75c4, 02:45:22, HundredGigE0/2/0/1
2001:218:0:1000::1/128 Remote ISIS 48d22h13m 18
For Hello PDUs, the "Interface Address" TLV MUST
contain only the link-local IPv6 addresses assigned to the interface
that is sending the Hello. For LSPs, the "Interface Address" TLVs
MUST contain only the non-link-local IPv6 addresses assigned to the
These are hello derived:
A:ytti at a04.chcgil09.us.bb# show router isis adjacency
r22.chcgil09.us.bb-re0 detail |match Neigh
IPv6 Neighbor : fe80::42de:adff:fe98:87e4
IPv4 Neighbor : 220.127.116.11
Vendors do not have the option to use GUA while being RFC5308 compliant.
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