Cisco 1721 static routing

In article , Larry wrote: :Forgive me if this is a stupid question...

Not stupid at all, just something that'll become second nature with a bit of experience with the device.

:We are a small company and have a 1721 that is the gateway to :our provider for our Internet service. We are currently not :using any routing protocols and have 1 static route to our :provider. I now have the need to add a ethernet card in the :extra slot to route to another company temporarily. The company :is located in the same building so it should be easy but since :I'm saavy I need to make sure I'm doing things right.

:Currently the routing info looks like the following:

:iproute 0.0.0.0 0.0.0.0 65.65.xxx.xxx :Which is our ISP's router.

:Assuming the other parties end of the connection is 172.16.17.1, :and I configure the address of Eth0 to 172.16.17.2, is this as :simple as adding the line:

:iproute 172.16.17.0 0.0.0.255 172.16.17.2

It's even simpler than that: you don't have to add any ip route statement at all. As soon as you assign the IP address and mask to the interface, the router will automatically add in a route out the Eth0 interface for all of 172.16.17.*. The devices at the other end of the link will take care of the rest.

:Are routes processed in order like ACL's? Does the new route :need to be first to be processed correctly?

Routes are processed as "longest match" first. Any traffic to 172.16.17 will match 24 bits to the automatic "connected" route that the router will put in for you, whereas traffic to other locations will not match that same prefix and will match only the

0-bits long default route that you have.

The more specific a route entry, the higher it's precidence; the order of the routing statements in the configuration doesn't matter. [Not, that is, until you get into policy based routing.]

Note: the above, saying that you don't need to add a route at all, presumes that the other end is not using a router between you and them. If they -are- using a router in between, then a route statement would be needed... e.g.,

ip route 172.16.18.0 255.255.255.0 172.16.17.1

{I'm going to skip the paragraphs of explaining that...}

Are you sure the 1721 supports an extra LAN card? My understanding is that those 2 WIC slots are WAN WIC for WAN modules.

Let's get back to your original question. If your partner is responsible for NAT'ting their networks, then your serial1 would

172.16.17.2/24. You need not a static route to their network (same subnet).

If they are not responible for NAT, AND their internal network that you want to access is 172.16.17.0/24, then you and your partner will need to agree to a new subnet (e.g. your serial1 is 172.16.18.2/30 and theirs is 172.16.18.1/30), and you'll set up a static route of together with the existing default route:

ip route 172.16.17.0 255.255.255.0 172.16.18.1 ip route 0.0.0.0 0.0.0.0 65.65.xx.xx (already existed, no need to re-enter)

Anything destination that does not match 172.16.17.0/24 and your internal networks would be routed to 65.65.xx.xx.

"Route Selecti> Forgive me if this is a stupid question...

In article , wrote: :Are you sure the 1721 supports an extra LAN card? My understanding is :that those 2 WIC slots are WAN WIC for WAN modules.

That's a good question; you merely happened to have overlooked the WIC-1ENET One-port 10BASE-T Ethernet interface .

Since they don't need to use VLANs on the link, and they are not trying to bridge the two ethernet interfaces, a "WAN" ethernet interface is the same as a "LAN" ethernet interface to them.

snipped-for-privacy@ibd.nrc-cnrc.gc.ca (Walter Roberson) wrote in news:d63j59$jt9$ snipped-for-privacy@canopus.cc.umanitoba.ca:

Very helpful... Thank you sir! Interesting to note that the mask for "iproute" is the same as a mask for your ip config on your PC. It's those details that keep me mixed up. I have a very detailed ACL that I use to help keep the garbage away from the firewall and the masks are just he opposite.

Again much thanks.

Larry

snipped-for-privacy@hotmail.com wrote in news: snipped-for-privacy@z14g2000cwz.googlegroups.com:

Absolutely positive. It is only 10BaseT but that is sufficient for our needs. We have used this router in just this scenario a couple of years ago which is why I chose this path, we already have the hardware.

That is exactly the case so I should not need to add anything over what is automatically added when configuring the interface.

I'll follow-up on that link in the morning.

Thanks again!