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OSPF

nappyshock
Occasional Visitor

OSPF

I have an issue with setting up ospf, i have a straightforward design with just area 0 and have 4 local switches and a number of remote switches connected with LES links, the remote switches are linked via a seperate point to point vlan's.
I have a number of vlans locally which i want distributed , when setting up the config have included them in the ospf area ie Vlan 2 - ip ospf area backbone etc . I also have routes to remote sites via an external MPLS network, when i look at the routes on my switches for example to a remote destination on the MPLS network, some switches show the route via the default vlan 1 ip others show it via the vlan 2 ip address. The show ip ospf neigbor command shows DR's and BDR's set up on different switches for different vlans, it all looks a bit of a mess.
What is the correct way to configure OSPF on a switch with multiple vlans that all require distributing around the network but only have all the communication and DR/BDR etc on one vlan, or is having DR/BDR on all the vlans normal.
4 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: OSPF

Hi

I just want to clarify one thing, do you have L2 MPLS or L3 one?

If you have L2, then you have to look again into your routes and the OSPF configuration.

If you have L3 MPLS, then what you should do is check if you have Traffic Engineering implemented somewhere forcing some traffic to exit via some Vlan.... etc.

Good Luck !!!
Science for Everyone
nappyshock
Occasional Visitor

Re: OSPF

The MPLS router is issueing the correct info, the problem is for example on a switch in the routing table a route to a remote site would be shown correctly as having the route via the MPLS router, but on some switches the route to the MPLS router is shown as via the vlan 1 ip address of the switch that the MPLS router is connected to and on others it is shown as via the vlan 2 ip address of the switch that the MPLS router is connected to. I just a bit confused as to why this is happening.
Olaf Borowski
Respected Contributor

Re: OSPF

Hi,
Depending on what switches you are using you have different options.
In general: only run OSPF on the VLAN that connects the sites for example the managment VLAN if you have multiple VLANs connecting the sites. To get the routes of attached networks advertised, do "redistribute connected" and the attached routes should show up. Another option would be to make the other interfaces "passive".
Let us know what switches you are using.

nappyshock
Occasional Visitor

Re: OSPF

The switches i have are 9300's and 5300's. I think i've found the issue but won't be able to check it for a while. The main Vlan1 has two ip addresses on it, the 9300's handle this ok however the 5300's i believe only include one of the ip addresses in the ospf assignment by default, you need to add the command "ip ospf all" under the vlan config.
I hope when i add this command it will resolve the problem.