[Info-vax] Routing when using two interfaces/networks.

[Kari Uusimäki]

On 17.1.2010 16:28, Jan-Erik Soderholm wrote:
> Hi.
> We have some hard-to-identify network problems at
> a site and I'm now thinking that it might have something
> to do with how the routing is setup in the VMS system.
>
> The VMS system (the "prod" system) has two interfaces :
>
> $ tcpip sh inter
>
> Interface IP_Addr Network mask
>
> LO0 127.0.0.1 255.0.0.0
> WE0 193.183.98.2 255.255.255.0
> WE1 10.32.137.1 255.255.255.0
>
>
> The 193.183.x.x is the "old" network that will be removed
> anytime(tm). The 10.32.x.x network is where most of the other
> stuff (term-servers, PC-clients and so on) are. Note that
> most other equipment on 10.32.x.x are on other subnets then
> 10.32.137.x. The only other host on the 10.32.137.x are mainly
> the other VMS systems. All "user" equipment are on other
> 10.32.x.x networks.
>
> The current routing looks like this :
>
> $ tcpip sh route
>
> DYNAMIC
>
> Type Destination Gateway
>
> AN 0.0.0.0 193.183.98.251
> AN 10.32.137.0/24 10.32.137.1
> AH 10.32.137.1 10.32.137.1
> AH 127.0.0.1 127.0.0.1
> AN 193.183.98.0/24 193.183.98.2
> AH 193.183.98.2 193.183.98.2
> st
> $ tcpip sh route/perm
>
> PERMANENT
>
> Type Destination Gateway
>
> PN 0.0.0.0 193.183.98.251
>
>
> The "dev" system has only one interface and looks like this :
>
> $ tcpip sho inter
>
> Interface IP_Addr Network mask
>
> LO0 127.0.0.1 255.0.0.0
> WE1 10.32.137.3 255.255.255.0
>
> $ tcpip sh rout
>
> DYNAMIC
>
> Type Destination Gateway
>
> AN 0.0.0.0 10.32.137.254
> AN 10.32.137.0/24 10.32.137.3
> AH 10.32.137.3 10.32.137.3
> AH 127.0.0.1 127.0.0.1
>
> $ tcpip sh rout/perm
>
> PERMANENT
>
> Type Destination Gateway
>
> PN 0.0.0.0 10.32.137.254
>
>
> The "problems" we are seeing are e.g. :
>
> - Troubles ("hangs") when FTP copying from "prod" to "dev".
> - Intermittent slow access from PC clients.
>
> My guess is that the disturbances are due to the fact that all
> routing goes through the 193.183.98.251 gateway, even between
> different 10.32.x.x subnets, right ? And that the solution
> probably would be to simply move the default router from
> the 193.183.98.251 gateway to the 10.32.137.254 gateway on
> the system with two networks ?
>
> Jan-Erik.
>
>
>

The default gateway should be the one which routes the most traffic. In 
this case the gateway at 10.32.137.254.

Nothing prevents you from adding network entries for the different 
193.*.*.* subnets which all are reachable through the gateway at 
193.183.98.251.

Of course you can do supernetting like said in another post. Provided 
that you don't have really old routers which don't understand supernetting.


Kari