Static default route question

[Mehmet]

Create a new VLAN on the HP switch and connect router2 to that VLAN. Give Router2 an IP of 192.168.255.1/255.255.255.252 and the HP switch 192.168.255.2 / 255.255.255.252. Configure a static default route on the HP switch to point to Router2's IP address. That will route all VLANs via Router2.

 

Leave Router1 connected to VLAN1 and set all devices on VLAN1 to use Router1 as its default gateway (it sounds like that's what you already have).

 

Put a static route on both routers to point each one back to the rest of the LAN via the HP switch's address on the relevant VLAN, so Router1 would have a static route pointing 192.168.0.0 / 255.255.0.0 to 192.168.60.2. Router2 would have a static route pointing 192.168.0.0 / 255.255.0.0 to 192.168.255.2.

 

You'll also need to enable IP redirects on the routers and HP switch if they support it.

 

Would this not result in ALL inter-VLAN traffic having to go through one of the two routers? In which case I would be concerned about the links becoming congested - or am I mistaken? I am not too sure about the validity of this design, but you probably know more than I do... just sounds to me like something which wouldn't be the recommended practice.

[gaiacraig]

No, they would just be gateways. However I do see where I was unclear.

 

The only connection between the network and Router2 would be on the new VLAN, so the existing VLANs configured on Router 2 would be removed and the HP switch would now be the router for ALL VLANs - it would adopt the IP addresses we removed from Router2.

 

As the static route on the HP switch is just a default route it would only route traffic to destinations where a valid route doesn't already exist on the HP switch. In turn, the HP switch would only send traffic to external networks to Router2.

[Mehmet]

No, they would just be gateways. However I do see where I was unclear.

 

The only connection between the network and Router2 would be on the new VLAN, so the existing VLANs configured on Router 2 would be removed and the HP switch would now be the router for ALL VLANs - it would adopt the IP addresses we removed from Router2.

 

As the static route on the HP switch is just a default route it would only route traffic to destinations where a valid route doesn't already exist on the HP switch. In turn, the HP switch would only send traffic to external networks to Router2.

 

I'm confused. When devices on VLAN 1 ARP for their gateway, which devices MAC address will they receive?

[gaiacraig]

As I said, all devices on VLAN1 would have Router1 set as their default gateway, so ARP would resolve the MAC of Router1 (We're not using proxy-arp where the clients don't have a gateway configured). In order to allow devices on VLAN1 to see devices on the other VLANs they need to know how to get to them, but as they're not using the router which deals with the other VLANs (the HP switch) as their default gateway they have to rely on Router1 to tell them (via the static route we configured and IP redirect). IP Redirect will tell the clients to use the IP address on the HP switch directly instead of routing traffic via Router1.

 

This explains a little...

Explanation of ICMP Redirect Behavior

 

Make sense?

[Mehmet]

As I said, all devices on VLAN1 would have Router1 set as their default gateway, so ARP would resolve the MAC of Router1 (We're not using proxy-arp where the clients don't have a gateway configured). In order to allow devices on VLAN1 to see devices on the other VLANs they need to know how to get to them, but as they're not using the router which deals with the other VLANs (the HP switch) as their default gateway they have to rely on Router1 to tell them (via the static route we configured and IP redirect). IP Redirect will tell the clients to use the IP address on the HP switch directly instead of routing traffic via Router1.

 

This explains a little...

Explanation of ICMP Redirect Behavior

 

Make sense?

 

Aha! That is clever!

 

Well, clearly I have a lot to learn.