On Wed, Apr 12, 2006 at 03:15:50PM -0400, Tim Donahue wrote: > I am having problems getting ospfd to work with 802.1q vlans. I have 2 > existing ospfd servers that are working correctly with physical interfaces in > each network they are trying to take part in. I recently built new box that > I'm trying to use vlans as it only has 2 interfaces and I want it to talk to > 3 different networks. When I start `ospfd -d` to see why no networks ever > get populated into the FIB I get the follow errors. Is there anything I can > do to resolve this problem? > > Tim Donahue > > recv_dd_description: invalid MTU 1500 sent by neighbor ID 10.4.64.3, expected > 1496 > if_fsm: event WAITTIMER resulted in action NOTHING and changing state for > interface vlan33 from DROTHER to DROTHER > recv_dd_description: invalid MTU 1500 sent by neighbor ID 10.4.64.1, expected > 1496 > > > # ifconfig > de0: flags=8863<UP,BROADCAST,NOTRAILERS,RUNNING,SIMPLEX,MULTICAST> mtu 1500 > lladdr 00:c0:f0:16:f0:5e > media: Ethernet autoselect (100baseTX full-duplex) > status: active > inet6 fe80::2c0:f0ff:fe16:f05e%de0 prefixlen 64 scopeid 0x2 > vlan33: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1496 > lladdr 00:c0:f0:16:f0:5e > vlan: 33 priority: 0 parent interface: de0 > groups: vlan > inet6 fe80::2c0:f0ff:fe16:f05e%vlan33 prefixlen 64 scopeid 0xf > inet 10.4.64.4 netmask 0xffffff00 broadcast 10.4.64.255
Welcome in the OSPF hell. OSPF requires that the MTU on all routers is equal or smaller then the own MTU (this ensures that you are able to receive all packets comming from that link). Now VLAN tends to reduce the MTU because of the VLAN header if you have a "crappy" ethernet card. Either you switch all interfaces that connect to your vlans to MTU 1496 or you modify your setup to be able to run a MTU of 1500 over your vlan links. Afaik all modern cards support these "oversized" frames for VLAN. Trivia: the MTU check was add to "fix" bro^Wtoken ring where it was possible to run with MTU/MRU combinations that made it impossible for two systems to exchange traffic correctly. -- :wq Claudio
