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HELP - How to connect two internal networks using cisco2620


We have two networks one on which has its own firewall and connected to internet and phone network on I am trying to use our old cisco 2620 with one fastethernet adapter to connect these two networks. First of all is it possible ??

I am trying with as primary and as

secondary IP for fa0/0 and have

route fa 0/0

Both the networks & router are connect to a switch.

I am not able to ping eitherside from the router. Please let me know what I am doing wrong.


New Member

Re: HELP - How to connect two internal networks using cisco2620

if both of your layer3 networks ( & are on the same layer2 network, your posted configuration should work. my assumption is that they are not on the same layer2 network, and this is where your problem lies.

please post more information about your layer2 network configuration and we should be able to figure this one out.

useful information would be:

- your switch config

- a topology diagram


Re: HELP - How to connect two internal networks using cisco2620

If both IP networks are on the same switch and that switch is configured for only one VLAN, then you should be able to configure a secondary IP address on the 2620's FastEthernet0/0 interface. Pings from the router should be direct to the destination hosts on either subnet. Maybe they're configured to not respond to pings? Check this by pinging from one IP to another IP on the same subnet.

Verify also that the IP addresses on the 2620 for each subnet are unique to the router. Duplicate IP addresses could cause problems with pings.

If that switch is configured for two or more VLANs, and each IP network is in a different VLAN from the other IP network, then it gets a little more involved. But your 2620 can route between the IP networks if you have a "Plus" version of IOS software on the router. That allows you to configure subinterfaces on the LAN interface, for example FastEthernet0/0.1, FastEthernet0/0.2, etc. You assign each subinterface to a VLAN; configure appropriate IP address information to each subinterface; and plug FastEthernet0/0 into a switch port that has been configured as a VLAN trunk port using 802.1Q tagging.

CAUTION: Keep in mind that the "Plus" version software usually requires more memory to run, and may require more flash memory to store the image file, compared to the regular IOS software.

What kind of switch is it?

Either way, the 2620 does not need a static route to the IP network if it is directly connected to it. It does, however, need a static default route that points to the firewall if people on the phone network want to get to the Internet.

And on the firewall, it's going to need to know how to reach people on the phone network via the 2620 router. A static route on it, pointing to the "remote" IP subnet with the 2620's LAN interface as the next-hop IP address, should do it for you.

The firewall may also need to be configured to translate those IP addresses on the phone network, in addition to the ones it already translates. What kind of firewall is it?

And the users on the LAN that can go to the Internet, may either have to change their IP default gateway to be the 2620 so they can get to the IP addresses on the phone network; or you could keep the firewall as the default gateway, and then configure static routes on the users' computers to find the "remote" IP subnet via the 2620's local LAN IP address as the next-hop.

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