Solved: Help on HSRP please

wayneneesam · ‎12-31-2013

Hi All,

I am trying to design a network for college course and I was told to look at HSRP for redundancy which I have got working using an interface on each router. (see diagram below). However what I want to do is connect my switches to both routers as at the moment each switch is currently attached to its own router. The reason I want to do this is so that if ManchesterSwitch3 was to go offline and Manchester1 router was to go off line then the whole network is off line. Hope this makes sense as I am fairly new to this. Thanks in advance.

Jon Marshall · ‎01-01-2014

Wayne

What you already have is usually accepted as good enough. The failure of 2 devices at the same time is considered a rare event and your network design is considered redundant as it is as a failure of one device does not mean that you lose network connectivity.

If you want to conect both switches to both routers then you run into the problem that 2 ethernet interfaces on the same router cannot use the same IP subnet. You could in theory use bridging on each router ie. the 2 ethernet interfaces are bridged and you apply the IP + HSPR config to the BVI (Bridged Virtual Interface) but i have not seen this done in a production network.

Note also that a common design in production networks is to use L3 switches for the routing and then you can connect the routers to both switches using L3 point to point links.

Is part of the design requirement that you must take account of 2 devices failing at any one time ?

By the way, please don't post the same question multiple times, once is good enough

Jon

View solution in original post

Jon Marshall · ‎01-01-2014

Wayne

What you already have is usually accepted as good enough. The failure of 2 devices at the same time is considered a rare event and your network design is considered redundant as it is as a failure of one device does not mean that you lose network connectivity.

If you want to conect both switches to both routers then you run into the problem that 2 ethernet interfaces on the same router cannot use the same IP subnet. You could in theory use bridging on each router ie. the 2 ethernet interfaces are bridged and you apply the IP + HSPR config to the BVI (Bridged Virtual Interface) but i have not seen this done in a production network.

Note also that a common design in production networks is to use L3 switches for the routing and then you can connect the routers to both switches using L3 point to point links.

Is part of the design requirement that you must take account of 2 devices failing at any one time ?

By the way, please don't post the same question multiple times, once is good enough

Jon

wayneneesam · ‎01-01-2014

Hi John,

Sorry for posting more than once, I have never really used forums before and I wasn't sure it had gone through properly.

The design requirement did not say anything about 2 devices failing at the same time. I am new to this and I am not really sure what is considered good enough and I agree it is highly unlikely that 2 devices would fail at the same time on the same network.

I suppose I just needed some guidance as to what is considered acceptable. I was trying to make it that if a switch and a router went down then the network wouldn't go down. I have not used layer 3 switches in my course yet so I will go with what I have now.

Thank you

Wayne.

Jon Marshall · ‎01-01-2014

Wayne

Sorry for posting more than once, I have never really used forums before and I wasn't sure it had gone through properly.

No problem at all.

Jon