Network Routing

[linuxwiz54]

Hopefully someone can guide in me in the right direction, I have 2 GBIC connected to the router 7301 from switch 4506, gave inteface g0/1 and g0/2 different ip address., what I am trying to accomplish is If I pull one gbic out I dont want the entire company losing internet connection. how can I configure it so I pull one out there is still working and has internet connection.

James.

[Richard Burts]

James

You have told us a few things but not enough for us to adequately understand your environment or to be able to offer much advice. Can you provide more information about router interfaces connected to the switch? You have that gi0/1 and gi0/2 have different ip addresses but do not tell us whether they are in the same subnet or in different subnets.

 The usual Best Practice to provide redundancy with a single router would be to have two router interfaces connecting to inside and other interface(s) connected to outside. The two interfaces connected to inside would connect to switch interfaces in different vlans and in different subnets. It would use a dynamic routing protocol running over both router interfaces connecting to inside. The 4506 would have ip routing enabled and would run the dynamic routing protocol over both interfaces that connect to the router. In this way the router can advertise routes to outside (at least a default route) over both links to inside and the router would learn the subnets that are in the inside environment over both links. This would provide load balancing when both links are operational and would provide automatic failover if one of the links has a problem.

Of course with a single router connecting to outside there is a single point of failure. And with a single 4506 connecting to the router there is another single point of failure. So the redundancy that you have provided is not very robust.

HTH

Rick

[linuxwiz54]

Hey Richard,

That's why I am on this form, asking for directions. I will do my best to explain.

router (7301) g0/1 interface connected to switch(4506) interface g1/1 with an IP address 192.168.10.x

router (7301) g0/2 interface connected to switch (4506) interface g1/2 with an IP address 192.168.20.x

I know best practice is  to have another router but company is not willing to shell any money for another router.

they want me to configure in a way if I pull one gbic out, entire company doesn't loose connection to share/outside world and so how do I configure it so both gbic or hot hot.

Hope this helps.

James

[Joseph W. Doherty]

Believe, from what you've described, you have two options.  You might configure the two links into an Etherchannel or you could configure routing to/from your 7301 that both links are possible.  Then if you disconnect either, your internet connectivity should remain via the one link.

BTW, as Rick already mentioned, this would provide little additionally redundancy.  Also BTW, if you can move the one port, on the 4506, to another line card, that would also slightly increase your redundancy.

[linuxwiz54]

Thank you Joseph, I understand, I have limited option, company upper management idea not mine, If I had my choice I go your guys route,

how do I configure that what are the command set it up.

[linuxwiz54]

Hi Richard,

How do I setup the dynamic routing, what command should I use to setup this up.

James.

[Richard Burts]

James

Based on what you have described it should be fairly straightforward to implement a dynamic routing protocol. The first step would be to choose which routing protocol to use.  There are several options but for this discussion I will assume that you choose EIGRP. Also I assume that the router has a static default route configured for access to the Internet. So you will want to redistribute that static route into EIGRP. The config might look something like this:

interface gig0/1

ip address 192.168.10.1 255.255.255.0

interface gig0/2

ip address 192.168.20.1 255.255.255.0

router eigrp 51

network 192.168.10.0

network 192.168.20.0

Redistribute static metric 10000 100 255 1 1500

This should work fine if there is a single static route. If there are multiple static routes on the router then you need to decide whether you want to advertise all statics or advertise only the static default route. If you want to advertise only the static default then you would need a distribute list or a route map to control the redistribution.

You would want a similar configuration on the 4506.

HTH

Rick

[Richard Burts · Accepted solution]

James

Thanks for the additional information. It is good to know that the two router interfaces are connected to two switch ports and that different IP addresses/different subnets are being used. This is what I was describing in my previous post. If you enable ip routing on the 4506, configure a dynamic routing protocol to run between the router and the 4506, configure the routing protocol to use both links, then it should do equal cost load sharing. This will mean that both links are being used when both are available. And it will mean that if one interface goes down (a gbic is pulled) then all traffic will use that link that is still up.

HTH

Rick