Routing with HSRP

[Jimtron26]

Hi all,

I have two routers on a network. Each router is configured for router-on-a-stick inter VLAN-routing.

VLAN 1 192.168.42.0/24
VLAN 2 192.168.43.0/24

HSRP is active between the two routers which are addressed in each VLAN as follows

R1
fa 0/0 MAC 11-11-11-11-11-11
fa0/0.1 IP 192.168.42.253
fa0/0.2 IP 192.168.43.253

R2
fa0/0 MAC 22-22-22-22-22-22
fa0/0.1 IP 192.168.42.254
fa0/0.2 IP 192.168.43.254

HSRP Group 1 Address: 192.168.42.1
HSRP Group 2 Address: 192.168.43.1
HSRP MAC: 33-33-33-33-33-33

R1 is the Active router.

I have a Client on VLAN 1, IP address 192.168.42.x DG 192.168.42.1.
I have a Web Server on VLAN 2, IP address 192.168.43.50 DG 192.168.43.1

In this scenario, Client can ping and connect via HTTP to the Web Server routing by their default gateway's which is
Router R1 (Active router). All working nicely.

If R1 fails, R2 becomes active and therefore the scenario continues to run OK as the gateway has simply switched to
the other router.

Now:

Change default gateway on Client 192.168.42.x to 192.168.42.254 (Standby router).

In this scenario, Client can ping the Web Server but cannot connect via HTTP, the page times out.

When the Client sends packets to the Web Server 192.168.43.50 address, it has to ARP for the default
gateway MAC address and forms it's packets with following destination addresses:

IP: 192.168.43.50
MAC: 22-22-22-22-22-22 (R2 MAC)

However, it returns with source addresses of:

IP: 192.168.43.50
MAC: 11-11-11-11-11-11 (R1 MAC)

I understand why this is so however;

1. Why does the ping succeed but the browsing fails..? is this becuase a HTTP connection forms a session between the two whereas the ping is merely sent as a reply?

2. Is there a way around this, without changing the gateway on the client back to the .1 address?

Any thoughts and ideas most appreciated

PS (I haven't posted any configs because I am not sure they would help with what is really a theory question and
not an incorrect programming issue but can supply if needed)

Many thanks

Jim
CCNP

 

[unclerico]

my question is why are you changing the client default gateway?? when router a fails, router b will assume the VIP and V-MAC of the group. maybe i'm missing something with your question??

I hate all Uppercase... I don't want my groups to seem angry at me all the time! =)
- ColdFlame (vbscript forum)

 

[Jimtron26]

Hi unclerice, thank you for your response

The reason in this instance for changing the DG is for testing purposes. There is an ADSL connection on both of the routers, to test incoming web etc on the .253 router, then I can get out on the ADSL connected to the .254 router and back in again, as if I am an external user. If I do this however, I cannot open web pages, telnet sessions in the 192.168.43.0/24 subnet.

I also have an install coming up where this scenario will be implemented ie 2 routers/ 2 VLANs however it is going to span multiple sites and the customer wants to be able to communicate with devices across the "secondary" connection however, these devices are going to have a DG of the primary connection...

I don't think it is going to be possible unless the devices have their DGs set to the secondary router and was just wondering if anyone had an explanation for it...

Many thanks

 

[brianinms]

I would have to see both router configurations before I could offer an explanation.