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3800 - Enabled IP Routing = Lost Comms

Amtiskaw
Occasional Advisor

3800 - Enabled IP Routing = Lost Comms

Hi -  I'm setting up an HP E3800-48G-4SFP+ running KA.15.03.3006

 

Each time I enable IP routing I lose my SSH session, and have to mosey over and disable routing via the console port.

 

I have vlan1 disabled, vlan 7 as management and vlan 34 for data.

 

Show ip gives me:

 

VLAN                IP Config    IP Address       Subnet Mask      Std   Local

------------------------------------------------------------------------------------------

Default             Disabled

Management  Manual        10.40.0.5          255.255.255.0   No   No

10.20.34.0       Disabled

------------------------------------------------------------------------------------------

 

10.40.0.5 is vlan 7

10.20.34.0 is vlan 34

 

show IP route gives me:

 

Destination      Gateway           VLAN  Type             Metric   Dist

---------------------------------------------------------------------------------

0.0.0.0/0           10.40.0.1          7          static            250      1

10.40.0.0/24    management   7         connected   1           0

127.0.0.0/8       reject                             static            0          0

127.0.0.1/32     lo0                                 connected  1           0

-------------------------------------------------------------------------------

 

10.40.0.1 is the vlan7 interface on our 8200zl core switch.

On the 3800, uplink port 1/52 (fibre) is tagged in vlan 7, as is the port on the 8200zl core this links to.

 

What am I doing wrong here?

 

 

4 REPLIES
Amtiskaw
Occasional Advisor

Re: 3800 - Enabled IP Routing = Lost Comms

Another question - why is the metric so high for the default gateway? I've tried editing the 0.0.0.0/0 route, but it won't let me use the metric command - all I can change is the next hop.

paulgear
Esteemed Contributor

Re: 3800 - Enabled IP Routing = Lost Comms

First guess: you're connecting from an address on VLAN 34 and it's being blocked because you have the management VLAN defined. Enabling a management VLAN blocks switch management traffic from all other VLANs.

Next guess:
- when IP routing is enabled, default gateway is set via "ip route"
- when IP routing is disabled, default gateway is set via "ip default-gateway"
You might have the latter set but not the former. But if you have a management VLAN enabled, this is irrelevant, since you can't route to the management VLAN.
Regards,
Paul
Amtiskaw
Occasional Advisor

Re: 3800 - Enabled IP Routing = Lost Comms

Hi Paul

 

Thanks for the reply. It was the default gateway becoming inactive when IP routing was eneabled. I added a 0.0.0.0/0 route and pointed it at the management vlan interface on the core 8200, and all is well again.

Blindingly obvious, now you've pointed it out...

 

I could always get to the management vlan - it has a vlan interface on the core, and an ACL only allowing access via the the IS depts vlan. Not much point having a management vlan if you can't access it!

 

Thanks again :-)

paulgear
Esteemed Contributor

Re: 3800 - Enabled IP Routing = Lost Comms

Glad to hear you got it working!

Regards,
Paul