LAN Redundancy

[Jason Biehl]

I am trying to figure out the best way to implement redundancy between my core switches and my

two Internet routers. I have two core switches and two Internet routers. The Internet routers are multihomed. I want to have one connection from each router to each core switch. I am unsure exactly how to effectively implement this setup. If there was a single multihomed router to two core switches I could use routed connections from the router to each core. However, with dual multihomed routers I am unsure the best approach to implement this configuration. I want to make sure if anything fails between the cores and the Internet routers that there will be no disruption in connectivity.

[lgijssel]

That is a complicated subject.

Hope you find the following link useful:

http://www.cisco.com/en/US/docs/solutions/Enterprise/Campus/routed-ex.html

regards,

Leo

[spremkumar]

Hi

As mentioned by leo its a very broad topic which deals the involvement of multiple protocols both in lan/wan and also depends on whether you own any ip address space or AS nos. Owning ip addressing space and the AS nos will help running routing (BGP) protocol with your isp which can take care of load sharing or redundancy. Again itnernally to your local lan you need to decide where to terminate your L2 domain and to start your L3 domain.

For an example there are couple of most widely used practices basically deals with spanning your VLANs onto the wan router and the second approach is to terminate the L2 vlans onto the switch and then proceed on with the L3 domain which actually gives you the liberty to run a routing (OSPF) protocol between your routers and the switch. This approach can help you out in deciding the forwarding path based on availability etc.,

regds

[lal.antony]

@Jason,

If you are just looking for a path to carryout more research, I think something like HSRP, GLBP and WAN redundancy is best topics to look. If you select one of these I can help in going into more details.

Below is articles might be useful for your research.

HSRP: http://www.cisco.com/en/US/tech/tk648/tk362/tk321/tsd_technology_support_sub-protocol_home.html

GLBP: http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6554/ps6600/product_data_sheet0900aecd803a546c.html

Maybe a combination of these might be the solution you are looking for.

Cheers

Lal Antony

http://www.lalantony.com

[sachin_sharma0021]

Hi Jason,

HSRP/VRRP/GLBP are best solution for Lan redundency. As well as you have to use IP SLA for tarcking of Link. Some times wan link goes down but its protocol & status show up.In this condition link is not shifted to another link. So best practice for this sitution is IP SLA.

Please go through the below links :- this would be very help to understand the IP SLA technique.

www.cisco.com/.../ip_sla/configuration/.../hsicmp.html - United States

Please rate me if i m right.