Default router and OSPF

[andrewrocks]

Hi,

I have attached a diagram that I hope explains the topology sufficiently. All the switches are 3560s and the router is a cyberoam.

The Switches are all connected using routed ports on layer 3. The router at the end has a static route for the entire 172.16/12 range which points back to the final cisco switch in the chain.

I have a static route set on the first switch for 0.0.0.0/0 172.20.1.10 which I thought would mean that any device using this switch as its default gateway would have it's wan traffic sent out of the router, however this isn't happening.

If I ping 172.20.1.10 from the server I get responses straight away. If I ping the server from the router then it works fine too. I can also ping the router from each of the switches and visa versa.

However, if I ping 8.8.8.8 from the server I get "172.31.254.106 No route to host".

I'm completely stumped by this as the route has been given to it already hasn't it? I'm even more confused as the final switch in the chain has the same static route in and pinging 8.8.8.8 works fine.

Does anyone have any suggestions?

Regards

Andrew.

[MUHAMMAD AZAM AMEER]

hey sandeep

i have and issue connecting two routers with a 2960 switch which is connected to the internet switch?

can you give me an EXAMPLE OF ANY CONFIGURATION TO CONNECT THE ROUTERS, THE ROUTERS ARE 3945 ROUTERS PLEASE

Help

[John Blakley]

Start a new thread please. I've seen this same post in 2 unrelated posts.

[smehrnia]

Hey Andrew,

which one of the switch'es are ur first and last one? is 8.8.8.8 a loopback interface or something? is it in the ospf process? or just considered an outside route (0.0.0.0/0) ?

what happenes here regarding to ur diagram and explainations is this:

you have ur Router and Server ip addresses up in ur routing tables via the ospf process and connected int, so u when ur network is sync, everyone can ping them all. the static route on ur Router points to its upstream switch.

about the network 8.8.8.8 you set a default route on ur switch pointing to the far end router, and none of the devices know about a default route. let's try this: set your Router to originate a default route via OSPF and see if it works.

plz Rate if it helped.

Soroush.

[andrewrocks]

Sorry, when I say "first" I meant the switch that the server is plugged into, when I said "last" I meant the last in the chain, i.e. the one the router is connected to.

8.8.8.8 is the google public DNS server which I am using to test internet access.

I'm afraid I don't quite follow your last point, could you please elaborate?

Thanks for your help

Andrew.

[smehrnia · Accepted solution]

are you running OSPF on router too? if yes,

remove the default route on ur switch. add this command under your router's ospf process:

router ospf X

default-information originate always

this way your router introduces itself as the default route for the network and everything would work fine

plz Rate if it helped.

Soroush

[andrewrocks]

Hi Soroush,

I see what you mean now, however I don't think this will quite give me what I want.

First of all, the router is not that clever, it doesn't support OSPF (hence the static routes on it).

Also, I want to be able to use differen default routes for the different switches on the network. The switches in this diagram are actually spread over three buildings and I want to be able to give them their own local WAN presentations at some point, but for now they will run from head office.

So everntually I need to be able to set this at the switch level, not just the OSPF level across all buildings.

Does that make sense?    

Andrew.

[smehrnia]

yeah i got u. look, there are a number of things you can do to have different static routes working together providing redundancy and stuff.

But, for your current situation (linear design) to work, default routes should point to ur your upstream gateways, aka Next-hop, yours points to an address on the other end of the net. So, correct ur config, put a default route on every switch pointing to their next hop, see if it works.

plz Rate if it helped.

Soroush

[andrewrocks]

Ah I see what you mean now, that makes sense.

If I were to set the "last" switch (172.20.1.1) as the OSPF default-information originate always as you stated and then this switch has a static route of 0.0.0.0 0.0.0.0 172.20.1.10 in it, would this then work? (this would save me having to manually set the default route on each device and would allow for ospf multiple paths to work)

Thanks again    

Andrew.

[smehrnia]

I believe it would work, devices send their unknown traffic to ur last switch, then your last switch forwards the unknown according to its own default route

PS: we usually Rate the helpful posts, so others can easilly find and use them as good info

CheerZ.

Soroush,

[andrewrocks]

I award ratings when I've tested it to make sure I don't send people on red-herrings.

I've tested this and it does indeed work, great stuff thank you so much.

Regards

Andrew.

[smehrnia]

Anytime!

glad it could solve the issue.

Soroush.