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Firewall Connectivity

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grapeola
Occasional Visitor

Firewall Connectivity

I have a feeling that this is an inane question but any assistance would be appreciated. I have a series of switches connected through a 6108 aggregator which routes between the various VLANs on the network. One of the switches connected to the 6108 is a 2848 which I have a little temporary firewall attached to. I've created a route on the 6108 to point all non-VLAN related traffic to the firewall address (0.0.0.0 0.0.0.0 10.1.1.5). The firewall, however, doesn't allow me to put in a gateway on the LAN interface, just the IP (10.1.1.5) and mask (255.255.255.0). Because of the lack of gateway (I think) the firewall's IP doesn't show up in the 2848's ARP table and therefore the 6108 has no idea where to send 10.0.1.5 traffic. How do I resolve this? I want all the VLANs to be able to talk to the firewall and the firewall to be able to route to all the VLANs. How is this done without a gateway on the firewall?

Thanks very much
3 REPLIES
Mohieddin Kharnoub
Honored Contributor

Re: Firewall Connectivity

Hi

Usually in this kind of solutions, and since the routing between Vlans is done on the 6108 switch, and to make all the Vlans talk to the firewall, a Route back for the the Vlans should be inserted in the firewall.

If you can attach the config of your 6108 switch, and what kind of firewalls you have ?

Good Luck !!!
Science for Everyone
grapeola
Occasional Visitor

Re: Firewall Connectivity

Thanks. Attached is the config for the 6108. I was attempting to use my limited networking experience to try to help someone out but Iâ m not involved anymore. For my own curiosity, however, I would like to continue with this dialog and turn this into a thought experiment. The firewall was a little Linksys DSL router that appeared to have some limitations as to what static routes I could make on it (for instance it wouldnâ t allow me to create a route for itself with a 255.255.255.255 mask). For the moment letâ s assume that I was using a device that allowed me to create whatever routes I would want. What would those routes be? Hereâ s my attempt. Perhaps someone could tell me if these would function or not.

10.1.1.5 255.255.255.255 127.0.0.1
10.1.0.0 255.255.0.0 10.1.1.1

Does the loop back address make sense? Do I need to create routes to each VLAN?
10.1.0.0 255.255.255.0 10.1.1.1
10.1.1.0 255.255.255.0 10.1.1.1
10.1.2.0 255.255.255.0 10.1.1.1
10.1.3.0 255.255.255.0 10.1.1.1
10.1.4.0 255.255.255.0 10.1.1.1

Also, I'm assuming that the routes would resolve the problem with 10.1.1.5 not showing up in the ARP table on the 2848. Is this the case?

Thanks very much
Mohieddin Kharnoub
Honored Contributor
Solution

Re: Firewall Connectivity

Hi

I checked the config of your 6100, and this is your scenario,

- your internet router/firewall is 10.1.1.5 and a default route in place and its correct.
- Vlan2 in the same subnet of the internet firewall.
- Routing between Vlans on the 6100 is enabled and you should have no problem.
- What you need now is 2 things :

1- Make sure you can ping the 10.1.1.5 (firewall) from the switch 6100, because i noticed that you tagged port 1-4 to all Vlans and i believe you need to untag the port connected to the firewall for Vlan2,
OR since your 2824 has the firewall be sure the its connected to untagged port to Vlan2 on the 2824.

2- Add the following static routes to the firewall:

ip route 10.1.0.1 255.255.255.0 10.1.1.1
ip route 10.1.2.1 255.255.255.0 10.1.1.1
ip route 10.1.3.1 255.255.255.0 10.1.1.1
ip route 10.1.4.1 255.255.255.0 10.1.1.1
ip route 10.1.5.1 255.255.255.0 10.1.1.1

I believe it will work, unless this Linksys has a limitation in NAT for different subnets, then i'm afraid that you have to change this router to an enterprise router/firewall.

Good luck !!!


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