[mrtg-developers] Re: MRTG over IPv6 tested with experimental Cisco IOS

[Lorenzo Colitti]

Rafael Martinez Torres wrote:

> Yes , the patch corrects the parser, but then I have the same problem
> when I try:
> 
> cfgmaker  --enable-ipv6 public@[2001:618:10:2a03:205:1cff:fe00:1df0]
> 
> --base: IPv6 libraries found, IPv6 enabled.
> --base: Get Device Info on public@[2001:618:10:2a03:205:1cff:fe00:1df0]:161
> SNMP Error:
> [...]
> Tell me whereis my mistake, please....

This is because the SNMP agent is replying using a different IPv6 
address than the one the query was sent to. This is what tcpdump shows:

> # tcpdump -nv -s1514 ip6 and port 161
> tcpdump: listening on eth0
> 13:47:37.168819 2001:760:4:0:204:76ff:fe22:5ba0.34475 > 2001:618:10:2a03:205:1cff:fe00:1df0.161: [udp sum ok]  { SNMPv1 { GetNextRequest(26) R=-1263143579  .1.3.6.1.2.1.1} }  (len 49, hlim 64)
> 13:47:37.650208 2001:800:40:2a03:205:1cff:fe00:1df0.161 > 2001:760:4:0:204:76ff:fe22:5ba0.34475: [udp sum ok]  { SNMPv1 { GetResponse(108) R=-1263143579  .1.3.6.1.2.1.1.1.0="Linux lisa.consulintel.euro6ix.org 2.4.18-3 #1 Thu Apr 18 07:31:07 EDT 2002 i586"} }  (len 131, hlim 54)

cfgmaker is sending requests to 2001:618:10:2a03:205:1cff:fe00:1df0, but 
snmpd is replying from 2001:800:40:2a03:205:1cff:fe00:1df0. So cfgmaker 
doesn't see the reply.

But if I use the other address, it works fine:

> $ ./cfgmaker --enable-ipv6 public@[2001:800:40:2a03:205:1cff:fe00:1df0]:161 -o /dev/null
> --base: IPv6 libraries found, IPv6 enabled.
> --base: Get Device Info on public@[2001:800:40:2a03:205:1cff:fe00:1df0]:161
> --base: Vendor Id:
> --base: Populating confcache
> --snpo: confcache public@[2001:800:40:2a03:205:1cff:fe00:1df0]:161 Descr lo --> 1
> --snpo: confcache public@[2001:800:40:2a03:205:1cff:fe00:1df0]:161 Descr sit0 --> 2
> [...]


Regards,
Lorenzo

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