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New Member

VLAN Communications Issues

Please note the following scenario:

- Site A is connected to Site B over Dark Fiber

- Site A = 192.168.1.x

- Site B = 192.168.2.x

- Site A has two VLAN's configured on the switch (3560)

VLAN 2 = 192.168.1.x

VLAN 3 = 192.168.2.x

- Site B's switch has all of its Gigabit ports (1 - 26) configured to be in VLAN 3 on Site A's switch (including the access port from Site B/Switch B to Site A/Switch A)

- Did not configure Switch B with IP routing functionalities as the entire switch is in VLAN 2 and you do not need to enabled routing within a VLAN, right?

- placed a laptop on both ends with IP's respective to that subnet (or VLAN 2)

- made sure the ports were in VLAN 2

- tried to ping each other over the fiber, ping did not work

- Ping did not work from clients

- Ping did not work from switch to switch

- I can not telnet to management IP for the switch in Site B

- however, "sho CDP neigh details" sees the swtich over fiber

- this scenario worked when I configured a test run of this set up via ethernet cable in my lab

- Can someone explain to me what I am missing? I am sure it is some small.

Thank you very much

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Bronze

Re: VLAN Communications Issues

Jonathan,

From the config you posted:

SwitchB:

interface Vlan1

description Management_IP_For_SiteB_Switch

ip address 192.168.2.11 255.255.255.0

SwitchA:

interface Vlan2

ip address 192.168.2.3 255.255.255.0

ip helper-address 192.168.2.10

Do you see the problem there ? :)

You created a management interface on SwitchB but associated the ip that belongs to VLAN2.

That's the reason after assigning an IP within 192.168.2.0 /24 subnet to VLAN2, you are able to ping.

You have ip routing enabled on switchB and if you want to treat this switch as an access switch, I recommend typing

(config)#no ip routing

Please rate helpful posts.

Thanks

11 REPLIES

Re: VLAN Communications Issues

Hi,

There's a contradiction in your posting. You say all ports in switchB is on VLAN 3 but all the other subsequent statements indicate the SiteB/SwitchB is on vlan2. Is this a typo or error in config. Can you clarify?

HTH,

Sundar

New Member

Re: VLAN Communications Issues

sorry about the mistake in explaining my issue

- Site B/Switch B ports are in VLAN 3 (192.168.2.x)

- Site A/Switch A is configured with two VLANS

- VLAN 2 = 192.168.1.x

- VALN 3 = 192.168.2.x

- Laptops have been placed in a Gigport on Site B/Switch B (lets say Gi0/3 VLAN 3)

- placed laptop on Site A/Switch A in a Gigport (lets say Gi0/3)

- in addition I configured Site A/Switch A Gi0/3 to partake in VLAN 3 (192.168.2.x)

- gave IP addresses to both laptops x.2.16 and x.2.17

- no ICMP communication between the two however the interface registers input and I think output packets.

Does this help clarify things?

Silver

Re: VLAN Communications Issues

Hello,

Since you have multiple VLANs on Site B switch you have to configure the fiber interface as trunk. Once you configure it as trunk you can pass traffic.

Let me know if this helps and rate plz,

New Member

Re: VLAN Communications Issues

M-Haddad,

Site A is configured with multiple VLAN's Site B is not. I am very sorry for not explaining as succinct as possible (I am not test writer that's for sure). So sense Site A/Switch A has multiple VLAN's I have to configure it to Trunk? Hmmmmm. Why would I need to Trunk the access link up to Site B/Switch B when ICMP communication is only taking place in one VLAN (vlan 3) and not outside of it. Please help me understand. I did not have to do this during my testlab scenario. Other than making sure ports were in its necessary VLAN, everything worked fine.

Re: VLAN Communications Issues

Can you post the following output from both switches.

1. show vlan

2. show run int g0/3

3. show int g0/3

4. show int vlan3 on switchA & show run int vlan3

Are the PCs the configured with the correct default gateway address, 192.168.1.x?

Silver

Re: VLAN Communications Issues

Well, as long as I understand on Site B all ports are on the same VLAN3. And you set the port going to Site A on vlan3 as well. Same for the port going from Site A to Site B you set it on VLAN3.

Is that right?

Can you paste the config for switch in SiteA and B

New Member

Re: VLAN Communications Issues

Please take a look at the config file to see if I am mistaken or missing something in my configuration.

Thanks

Re: VLAN Communications Issues

Do you have vlan 2 created in both switches. Can you post the output of show vlan on both switches?

Is the gig interface up between the switches up and do you see input/output packets on them?

New Member

Re: VLAN Communications Issues

After performing a side by side comparison of the config files i determined that SiteB/SwitchB did not have an IP address associated with VLAN 2. Once I configured an IP address on SiteB/SwitchB for VLAN 2, that was in the same range as was in the same IP range for SiteASwitchA IP address. I was able to send ICMP packets from the client on Switch B/Site B to Switch A/Site A. I did not think I had to do that. Can anyone explain to me why?

Hall of Fame Super Bronze

Re: VLAN Communications Issues

Jonathan,

From the config you posted:

SwitchB:

interface Vlan1

description Management_IP_For_SiteB_Switch

ip address 192.168.2.11 255.255.255.0

SwitchA:

interface Vlan2

ip address 192.168.2.3 255.255.255.0

ip helper-address 192.168.2.10

Do you see the problem there ? :)

You created a management interface on SwitchB but associated the ip that belongs to VLAN2.

That's the reason after assigning an IP within 192.168.2.0 /24 subnet to VLAN2, you are able to ping.

You have ip routing enabled on switchB and if you want to treat this switch as an access switch, I recommend typing

(config)#no ip routing

Please rate helpful posts.

Thanks

New Member

Re: VLAN Communications Issues

Ed,

As usual you are correct. I do not know, how I could have overlooked something as minor as that. As you stated, I:

- disabled ip routing

- I changed mgmt VLAN IP address

- Switch B is now an access Switch instead of a routing switch. Thanks Ed (what took you so long anyway...lol)

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