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New Member

3750 vlan routing issues

I have 2 3750s configured in a stack with 2 vlans - vlan 1 and vlan 99. I have setup inter vlan routing which works fine. I have been trying to get a default route to the internet to work using a routed port to no avail. I have set my workstation to have a def gw of the vlan interface and can ping across the vlans, but cannot ping to the routed port.

The issue is that the routed port cannot be on the same vlan as vlan1 (which it is in production currently, ie route should be 10.61.30.2) so I added a subinterface to the router (10.61.38.1) and used a different network address on the routed port (10.61.38.x). This doesnt work as the arp tables dont seem to resolve?

Any thoughts?

I've attached the switch config

9 REPLIES
Hall of Fame Super Bronze

Re: 3750 vlan routing issues

So, you can't ping 10.61.38.2 from the switch ?

Can you post the output from typing

show ip int bri | ex una

and

show interface FastEthernet1/0/11

In order to ping out to the internet, a device needs to have NAT enabled. I'm assuming that's the function of 10.61.38.2 ?

New Member

Re: 3750 vlan routing issues

No, i cannot ping 10.61.38.2

Heres the dumps

nterface IP-Address OK? Method Status Protocol

Vlan1 10.61.30.10 YES NVRAM up up

Vlan99 10.61.39.1 YES manual up up

FastEthernet1/0/11 10.61.38.1 YES manual up up

FastEthernet1/0/11 is up, line protocol is up (connected)

Hardware is Fast Ethernet, address is 001a.6d59.6442 (bia 001a.6d59.6442)

Internet address is 10.61.38.1/24

MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

Keepalive set (10 sec)

Full-duplex, 100Mb/s, media type is 10/100BaseTX

input flow-control is off, output flow-control is unsupported

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:21, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 9000 bits/sec, 11 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

46990123 packets input, 3864749185 bytes, 0 no buffer

Received 239680 broadcasts (0 IP multicast)

0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

0 watchdog, 35620 multicast, 0 pause input

0 input packets with dribble condition detected

51042458 packets output, 615457305 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 babbles, 0 late collision, 0 deferred

0 lost carrier, 0 no carrier, 0 PAUSE output

0 output buffer failures, 0 output buffers swapped out

melsw02#bble condition detected

sh ip arp

nternet 10.61.38.1 - 001a.6d59.6442 ARPA FastEthernet1/0/11

Internet 10.61.39.1 - 001a.6d59.6441 ARPA Vlan99

Internet 10.61.38.2 0 Incomplete ARPA

Hall of Fame Super Bronze

Re: 3750 vlan routing issues

Do you have access to the device 10.61.38.2 ?

What kind of device is it ?

Based on the interface output, it seems you have a large amount of traffic transiting this interface, however the counter has never being cleared. Was this interface used for another connection before ?

Re: 3750 vlan routing issues

have you checked the duplex settings of both the router and the 3750? check the cable also.

New Member

Re: 3750 vlan routing issues

device is a cisco 1841 router

yes the interface has been used before, i have not cleared the counters and due to the fact it drops a portion of the network when i enable the routed port, i have had to revert it back to a switchport.

Hall of Fame Super Bronze

Re: 3750 vlan routing issues

Can you ping the routed port from the 1841 router ?

Can you post the show interface output from that router ?

Once you go into L2 mode on the switchport, are you able to have bi-directional communication ?

New Member

Re: 3750 vlan routing issues

What's relevant about this question?

New Member

Re: 3750 vlan routing issues

My config is very similar to http://www.cisco.com/en/US/tech/tk389/tk815/technologies_configuration_example09186a008015f17a.shtml

I have 2 VLANs on a 3750, VLAN1 and VLAN99. VLAN1 is 10.61.30.1 and VLAN99 10.61.39.1. IP routing is enabled and a default GW on switch is 10.61.38.2.

The default GW on the switch should be 10.61.30.2, but i cannot use this as its the same IP range as VLAN1. So I have setup a routed port on my switch with a new subnet, 10.61.38.0 and setup a subinterface on the 1841 router of 10.61.38.2.

From VLAN99 I cannot ping the 10.61.38.2 router at all.

Hope that makes it clearer?

New Member

Re: 3750 vlan routing issues

can you ping the router when you source it from the routed interface?

ping 10.61.38.2 source fa 1/0/11 form enable mode

Does the router have a route back for vlan 99?

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