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Default Gateway

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jmotsinger

Technical User
Mar 5, 2004
21
US
If I am at the Central Office and there are (4) Cisco 2501 routers, one for each remote site. How do I configure the default gateway on the host PC's at the Central Office?

Thanks,
Jeremy
 
Does your Central office have Internet access? If so is then I assume there is a router that connects to an ISP. Your default gateway for all Central Office PC's should be that ISP router.

If you don't have Internet Access then you may not even need a default gateway unless you would rather point all default traffic to a particular remote office. More network layout info needed.
 
This is a difficult one. Normally a LAN is set up so that one router acts as the definitive router and connects the LAN to any remote sites (in many cases this is the internet gateway). You however have 4 routers, so you have various options.

1) You could choose one router as definitive if all four routers exchange routing information. If we call the routers routerA, routerB, routerC, and routerD connecting to sites A, B, C and D, and you choose routerA as the definitive router it must know about all routes handled by the other 3 routers or have static routes set up to sites B, C and D. If this is not the case traffic on the LAN for sites B, C and D will never find the route. The main downside would be that all traffic to sites B, C and D would travel through routerA and all return traffic would not as each router has a LAN interface, this can lead to confusion.

2) Give each Workstation and Server static routes for all sites via their respective routers. This is likely to be an administrative nightmare though.

3) Have all workstations and servers listen to and learn but not participate in the routing conversations, preferably via RIPV2 or OSPF but not via RIP v1. This would solve the issue but would be difficult to manage and has several perilous pitfalls such as lack of support for anything other than RIP in some OS's.

4) A layer 3 switch, this would be the best option, create a port based VLAN for the 4 routers and a port based VLAN to connect to all switches and hubs on the LAN. The L3 Switch would provide Def gateway from the LAN VLAN subnet IP address and route all traffic to and from sites via the router VLAN. This solution may sound expensive but need not be as there are cheaper L3 Switches out there now that will talk to Cisco routers (as long as they share a common routing Protocol). This solution would require changing the IP interfaces on the routers for the router VLAN and adding the def gateway address for all LAN hosts but that is all.
 
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