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I've been tasked with upgrading our network and could use some input. We have 2 networks coming in currently to a single C7206VXR. We are now adding a second 7206 and wish to use it properly to better balance our traffic and add some much-needed redundancy. We have a distribution layer consisting now of 5 Dell PowerConnect 5224s, which are replacing 100M C3500s.

Each 7206 has a PNE-G1 w/3 gigE ports, plus 2x PA-GE GigE and 2x 100M Ethernet cards.

General idea:

[net1]     [net2]
   |         |        <- NPE-G1 port
[7206] <-> [7206]
   |         |        <- PA-GE port
[sw1 ]       |
 [sw2 ] <----+
  [sw3 ]
   [sw4 ]
  1. Should I connect each incoming network to a separate 7206, then cross-connect the 2 7206s? If so, should I advertise the routes between the two dynamically or by using static routes?

  2. At the distribution layer I am placing 2 switches in each of our 2 cabinets. How should I connect the 2 7206s? I initially though about designating a network to each switch, but should I instead just cascade all the switches and connect each 7206 to a different switch? OR, since I have 5 gigE ports on the routers, should I connect all the switches directly to the routers?

My goal is to use each of the components as efficiently as possible.

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  • Normally, you only have one or two distribution switches, to which the access switches connect. Can these four distribution switches be stacked? – Ron Maupin Oct 10 '16 at 17:03
  • Are you running BGP with your ISPs, or do you only have default routes? – Ron Maupin Oct 10 '16 at 17:05
  • Hey Ron. No, BGP is a whole other issue. Currently default routes. At some point I need to get this piece in. – AaplMike Oct 10 '16 at 17:07
  • They can be stacked, which I now think would be the best. They'd be presented as one giant switch then, correct? If so, I could use VLANs to assign ports to networks, yes? It just boils down then to the best way to connect the edge routers to the switches so that if I lose a router, I can still keep the LAN up. – AaplMike Oct 10 '16 at 17:08
  • Yes. Are they layer-3 switches? If so, you can handle all the LAN routing on them, leaving the WAN routing to the WAN routers. – Ron Maupin Oct 10 '16 at 17:10
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Since you can stack the four switches to look like a single switch, that would be a good thing to do. It greatly simplifies things.

You probably should connect the two WAN routers to each other, then you can run a routing protocol between them, and it can route traffic from one to the other without needing to go through a user VLAN and the switch(es). With default routes, you want the primary router to have a lower AD than the other on the default route. Run a routing protocol between them, and configure HSRP or VRRP on the VLANs with tracking of the WAN link for failover to the other router.

Connect each WAN router to a different switch in the stack.

Connect the access switches with a connection to each of two separate switches in the stack, and you can channel the links together. This is much, much faster to converge in a failover situation; it doesn't need to wait for STP to converge.

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  • As for connecting the two 7206's together, would I just use a /30 between two unused ports and let RIP figure out the routes on the other sides? – AaplMike Oct 10 '16 at 18:45
  • You can use a /30 if you are more comfortable with that, but Cisco fully supports the /31 for point-to-point links that was allowed by RFC 3021. You probably want to use OSPF, rather than RIP. If do you use RIP, make sure it is configured as version 2 with no auto-summary. – Ron Maupin Oct 10 '16 at 18:49
  • What do you think about using BGP in the 7200 and just trunked etherchannel between the 7200s and down to the switches? – AaplMike Oct 10 '16 at 22:01
  • You don't trunk between routers, you trunk between switches. You only need a single link between the routers, but you must create subinterfaces using dot1Q to the switches for the VLANs. You could use iBGP, but I would only do that if you are really going to get eBGP connections to the ISPs. If you are just going to keep default routes, then iBGP is really too much for just two routers. You are better off with something like OSPF because it can automatically use a link cost to determine the best path in the case of a link failure. – Ron Maupin Oct 10 '16 at 22:06

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