ospf database size - affects that underlying transport mtu might have
This is a *single area* ospf environment, that has been stable for years.. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ? .and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing -Aaron
On 11/22/17 9:51 AM, Aaron Gould wrote:
This is a *single area* ospf environment, that has been stable for years.. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network
Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? > I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ?
Yes. Easy to check with a ping sweeping a range of sizes and DF set.
and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing
Not likely. How many routers and are things relatively stable in terms of routes changing? -- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV
This is a *single area* ospf environment, that has been stable for years. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network
I have seen this in the lab before, was related to the size of the LSA.
Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ?
You can check this with a ping of your mtu size set with the df bit set
.and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing
If you have a large amount of routers in your area the LSA size will grow, we saw a problem in testing when we injected 2000 prefixes into the area and the OSPF neighbour would not come up. On a cisco router you can set 'buffers huge' as a work around. Richard
Em 22 de nov de 2017 3:53 PM, "Aaron Gould" <aaron1@gvtc.com> escreveu: This is a *single area* ospf environment, that has been stable for years.. But now suddenly is having issues with new ospf neightbor adjacencies , which are riding a 3rd party transport network Anyone ever experienced anything strange with underlying transport network mtu possibly causing ospf neighbor adjacency to be broken ? Yes, the neighbor state will loop between init/Exchange and it will never become Full. As others said, you need to test the MTU size without fragmentation and adjust in your L3 interface (ping with DF-bit). I'm asking if the underlying 3rd party transport layer 2 network has a smaller mtu than the endpoint ospf ip interface have, could this cause those ospf neighbors to not fully establish ? IMHO, Your transport network must support your Full 1500 bytes MTU. No one want to deal with fragmentation. They need to activate jumbo frames to sell L2 circuits. .and I'm also asking this if the single ospf area has grown large enough to cause some sort of initial database packet to be larger than that underlying 3rd party mtu is providing Its normal to have a LSADB bigger than MTU could support, and with correct MTU this is not a problem. Regards, Rafael
participants (4)
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Aaron Gould -
Jay Hennigan -
Rafael Ganascim -
Richard Vander Reyden