routes

IP Routes

Posted by robd on March 29, 2014
Networking / No Comments

Hi All,

Started at a new company recently and they’ve had a ongoing issues for ages where they could only access one of two switches in their server room if they were on the same subnet.

So Switch A was the problem switch and had a IP of 10.0.0.123,

Switch B they could access from anywhere and had a IP of 10.0.0.124.

My Computer had a IP of 192.168.111.1.

So initially I started thinking the issue was down to vlans as we have around 50 vlans and I kind of just presumed it would be a issue with cross vlan routing.  Well actually I was wrong.

Firstly I pinged both switches:

SwicthA – Can not ping.

SwitchB – Can ping.

Next Trace route (TraceRT from a win 7 PC)

SwitchA – Could not trace

SwitchB – two hop trace, Core switch then the switch.

Ok so what next…..Lets try the above from the switches (so after connecting to server on the same subnet I ran the tests):

Ping my PC:

SwicthA – could not ping,

SwitchB – could ping.

Trace route:

SwitchA – No route,

SwitchB – two hop route.

So after this I decided it must be a routing issue, as both switches could ping the core switch and both switches could trace route the core switch.  So lets have a butchers at the routing.

Switch A# show ip route

                                IP Route Entries

  Destination        Gateway         VLAN Type      Sub-Type   Metric     Dist.
  ------------------ --------------- ---- --------- ---------- ---------- -----
  10.0.0.0/8         DEFAULT_VLAN    1    connected            1          0
  127.0.0.0/8        reject               static               0          0
  127.0.0.1/32       lo0                  connected            1          0
  192.168.101.0/24   iSCSI-VLAN      1010 connected            1          0
Switch B# show ip route

                                IP Route Entries

  Destination        Gateway         VLAN Type      Sub-Type   Metric     Dist.
  ------------------ --------------- ---- --------- ---------- ---------- -----
  0.0.0.0/0          10.0.0.2       1    static               250        1
  10.0.0.0/8         DEFAULT_VLAN    1    connected            1          0
  127.0.0.0/8        reject               static               0          0
  127.0.0.1/32       lo0                  connected            1          0
  192.168.101.0/24   iSCSI-VLAN      1010 connected            1          0

 

Hold the phone, there’s no sodding return route to the core switch (10.0.0.2)

So I added the route like so:

Switch B# conf
Switch B (conf)# ip route-static 0.0.0.0 0.0.0.0 10.0.0.2
Switch B# write

And bobs your uncle it worked!!


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