No router advertisement in response to solicitation (IPv4)

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pdbuchan
DD-WRT Novice


Joined: 07 Jan 2012
Posts: 1

PostPosted: Sat Jan 07, 2012 20:59    Post subject: No router advertisement in response to solicitation (IPv4) Reply with quote
Hi guys,

I have a Cisco E3000 with the following firmware:

DD-WRT v24-sp2 (08/12/10) mega

My OS is Ubuntu Lucid Lynx.

I am trying to understand why the router does not respond with a router advertisement when I send out a router solicitation (using raw sockets).

I'm sending it to the "all routers" multicast address 224.0.0.2.

Wireshark capture below.

0000 01 00 5e 00 00 02 XX XX XX XX XX XX 08 00 45 00
0010 00 1c f6 80 00 00 01 01 21 42 c0 a8 01 74 e0 00
0020 00 02 0a 00 f5 ff 00 00 00 00

I've put XX where my MAC address was.

The packet looks essentially the same as one I'd get using

sudo icmpush -rts 224.0.0.2

0000 01 00 5e 00 00 02 XX XX XX XX XX XX 08 00 45 00
0010 00 1c 33 72 00 00 fe 01 e7 4f c0 a8 01 74 e0 00
0020 00 02 0a 00 f5 ff 00 00 00 00

which doesn't get a reply either.

The only differences I see are in IPv4 I.D., TTL, and checksum.

RFC 1256 says TTL should be 0x01 if destination is IP multicast, or >= otherwise. So I disagree with icmpush which uses 0xfe.

Does DD-WRT not respond to router solicitations?

I wasn't able to capture an IPv4 router solicitation in the wild to compare with.

Dave
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