switch at vlan 20 cannot communicate with vlan 10 (IP routing enabled)

[sj.heng]

Hi Guys 

Not sure if my information provided is sufficient. I met some problem trying to communicate between 2 vlan. Please assist to see if any config required is missing. thank you.

switch 4948 cannot communicate with vlan10

i have enable ip routing in core switch, i also tried adding default gateway in edge switch and adding static route in core switch but result still same.

[InayathUlla Sharieff]

Can you share the trunk config and other relevant configs from both the switches?

[sj.heng]

Cisco 3750

interface gi1/0/24 is connected to PC

interface Te1/1/2 is uplink to 4948

ip routing

interface GigabitEthernet1/0/24
switchport access vlan 10
switchport mode access

interface GigabitEthernet1/1/1
!
interface GigabitEthernet1/1/2
!
interface GigabitEthernet1/1/3
!
interface GigabitEthernet1/1/4
!
interface TenGigabitEthernet1/1/1
!
interface TenGigabitEthernet1/1/2

switchport trunk encapsulation dot1q
switchport mode trunk

interface Vlan1
no ip address
!

interface Vlan10
ip address 10.1.1.2 255.255.255.252

!
interface Vlan20
ip address 10.1.2.1 255.255.252.0

Cisco 4948

interface te1/49 is uplink to 3750

interface TenGigabitEthernet1/49
switchport mode trunk

!
interface Vlan1
no ip address
!
interface Vlan20
ip address 10.1.2.2 255.255.252.0

[paul driver]

Hello

Onthe 4948 disable ip routing and apply a default-gateway
On both switch's make sure you have the L2 vlans created in the vlan database

res

Paul

[sj.heng]

Hi 

IP routing is only enabled on 3750

i have also added ip default-gateway 10.1.2.1 on 4948

but it still the same, anything else that i might missed out ?  

[pwwiddicombe]

Do a "sh vlan" on both switches, and make sure expected vlans exist.

"sh ip route" on both, and make sure either routing or default route is as expected.

"sh ip int brief" to make sure you don't have any other IP addresses on the switch - i..e. a loopback - that might be your ping default address but isn't known.

Do an extended ping, and SPECIFY the source address of the known interface, if you have others that might have been found above.  If your 3750 is also connected to an extended network, it might happen to have additional addresses, that could be the default one, or have routing tables that misdirect the intended address elsewhere.

[Furose M · Accepted solution]

ip default-gateway wont take effect when IP routing is enabled. configure a default route in 4948 pointing to Vlan 20's IP address of Core or disable ip routing in 4948.

it will ping.

[Carlos Villagran · Accepted solution]

Hi!

Can you show us the show ip route added in the 4948 switch?.

It seems the switch is not actually routing to VLAN 10. 4948 switch needs a static route like this one:

ip route 10.1.1.0 255.255.255.252 10.1.2.1

Hope it helps, best regards!

JC

[sj.heng]

sorry for the late reply.

Yes guys, it was due to the missing static route in 4948

there was no "IP routing" command found in the config of 4948, and i thought it doesnt require static route with trunking enabled.

thanks all :)

[glen.grant]

  If you just trunked the vlan to the 4948 then a static route should not have been needed as the default gateway is on the 3750 .  Any ip address on the 4948 would have been just to manage the switch  and the ip default gateway command could have been used .