OSPF, 2 routers, 2 areas, one link

[m.sobolev]

Hello! Please help: we have 2 routers, 2 areas (0 and 10) and only one 10G link between them. Right now this link belong to area 0, so area 10 is discontigous.

What is the right solution for this situation?

[m.sobolev]

Good day.

It would be nice to hear more opinions!

[Marwan ALshawi]

although the idea is not very clear but lets try to narrow it down

first

in each of your L3 switches you see area 10 route of the other end as inter area route O IA ?

if this is the cause because of area 0 separating area 10 between the two switches

now the question is are you looking to see these routes as intra area route appears as only O in the routing table ?

if yes you could try creating a tunnel interface in each of your switches and put that tunnel interface under area 10 in both of your switches

lets see if this will help or not because i am not sure if this is what you looking for or not

Good luck

[m.sobolev]

You're right, on both switches I see area 10 routes as inter area routes (IA).

I think your proposal to make a tunnel will work, but something tells me that there is a better, maybe clever design.

Thank you!

[Marwan ALshawi]

if you are thinking about better design in this case you need to start think about redesign the OSPF areas

because what we trying to do here is fixing the design issue, that's way all the suggested solutions here are work around

now in term of design:

do you have any backdoor link ( backup link) between area 10 ?

if not and the only link you have is the one between the switches in area 0 then what's the problem if you see the route as O or O IA ?

i mean if there is no other links intra or inter area route will make No deference because either way the traffic has one path , however if you have other links in this case you need to tell us because the picture in this case will be differnt 

good luck

please rate the helpful post

[m.sobolev]

Yes, backup link is present:

Routes are "O IA"

[Marwan ALshawi]

ok

now i can see we have more than one topology you gave us

i will stick with the last one

however if we compare it with the first one

in the first one you have vlan 10 and vlan 20

now based on this topology

as you mentioned switch A and switch B located in differnt locations and as it shown they configured as HSRP

now if you have a host using switch A as the primary HSRP and switch A gose down how this host will use switch B as the gateway ?

i am thinking about the HSRP and vlan 10 in this topology

do you have any link L2 or L3 in Area 10 ?

the link to switch C still has no effect because it is in area 0 and you can make switch A - switch B preferred by changing interface cost - easy one -

i only need to under stand area 10 how this is designed physically and logically

then we can make a decision

[m.sobolev]

All switches are at different locations, so if switch A goes down, all hosts on this DC are unaccessible, and traffic flows must be rerouted to backup DC (B)

[Nagendra Kumar Nainar]

Hi,

From what I understood from diagram and other discussion is, you have 2 switches (A and B) connected through L2 trunk and have Vlan 10 in area 10 and some vlan x in area 0. With this, you will have 2 OSPF neighborship between these two switches. (One via vlan 10 on area 10 and other via vlan x on area 0).

So if you have any router/network connected to vlan 10 on any switch, it will appear as intra route on the other switch. Now can you explain, what you are trying to acheive?.

Regards,

Nagendra

[m.sobolev]

You are correct except one moment - vlan 10 is ospf passive interface and switches are making neighborship only using single interface belonging to area 0.

[Nagendra Kumar Nainar]

Can you explain what you are trying to acheive?.

Regards,

Nagendra

[m.sobolev]

Lests start again:

We have to sites, A and B, we need layer 2 between them because server A and server B must be in single L2 domain, so we use L2 trunk and HSRP to reserve gateway.

Site C have L3 connections with A and B, and we use OSPF for dynamic routing in this circle. Area 0 serves all cross sites links. Area 10 is servers farm (both A and B), lets say area 20 is for site C.

The question is: what is the correct OSPF design between site A and B?

[Marwan ALshawi]

ok then HSRP in the diagramnot valid option it has no effect

as long as this is the case i would say just leave as it is becuase if you changed the route of area 10 to be as intra area route using the tunnel method or any other method no deffrence you will have

as i mentioned either way the traffic will go through one path

good luck

if helpful Rate

[m.sobolev]

HSRP is needed by servers that must be placed in single L2 domain