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Community Member

hel for sw 2940!!

I have two 2940 switches conected by fiber (port 0/9. Port 0/9 is "trunk mode" in both. I've created two vlans Vlan1: ports 1-2-3-4 and Vlan2: ports 5-6. Port 7-8 are in mode TRUNK. VTP mode transparent and spt disabled in both. The ports of Vlan1 ann Vlan2 can comunicate betwen them in every switch and betwen switches. Ports 7-8 COMUNICATE ok WITH VLAN1 BUT NOT WITH VLAN2. If I change NATIVE VLAN in ports 7-8 to vlan2 then Ports 7-8 COMUNICATE ok WITH VLAN2 BUT NOT WITH VLAN1. (it´s impossible to reach both Vlans at the same time ....¿¿¿any idea?? Many Thanks

8 REPLIES
Bronze

Re: hel for sw 2940!!

Where do ports 7-8 go to? Do they terminate on the other 2940 or on another switch? Is the remote end of 7-8 configured with correctly? Are they running the same trunk encapsulation and native VLAN? Are modes negotiable?

Any relevant configs would help.

Silver

Re: hel for sw 2940!!

Ports 7 and 8 belong to the native vlan, vlan 1 by default. If you want to communicate with a different vlan, vlan 2 in this case you need a router. The Catalyst 2940 platform has no layer three capabilities. What you're looking for is Intervlan routing which can be accomplished by using an external router. Look on Cisco.com for router-on-a-stick.

HTH

Leon

* Please rate useful posts.

Bronze

Re: hel for sw 2940!!

You also said that stp is disabled on ports 7 and 8. Might be a good idea to turn that on in a CST fashion just in case both ports 7 and 8 lead to the same switch.

HTH

Community Member

Re: hel for sw 2940!!

to HTH...: I'm testing the switches. In SW2940 nº1 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 7). In SW2940 nº2 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 8). The connections are: PC(IP 192.168.242.111)----(Port8, trunk)SW2940 nº1(Port9, trunk)---(fiber)----(port9, trunk)SW2940 nº2(port1 to 4,Vlan1 and port5 to 8,Vlan2)----CODEC video IP with ethernet port and IP 192.168.242.1). Ping from the PC to CODEC is OK in end ports of Vlan 1 BUT no in Vlan2. I was thinking (it was an error)that this is a malfunction of the trunk port8, BUT across the Vlan1 and Vlan2 I can ping ok betwen both Switches (thas is the purpose of Vlans...). Many thanks for make me understand this.. justomparra

Community Member

Re: hel for sw 2940!!

Leon...: I'm testing the switches. In SW2940 nº1 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 7). In SW2940 nº2 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 8). The connections are: PC(IP 192.168.242.111)----(Port8, trunk)SW2940 nº1(Port9, trunk)---(fiber)----(port9, trunk)SW2940 nº2(port1 to 4,Vlan1 and port5 to 8,Vlan2)----CODEC video IP with ethernet port and IP 192.168.242.1). Ping from the PC to CODEC is OK in end ports of Vlan 1 BUT no in Vlan2. I was thinking (it was an error)that this is a malfunction of the trunk port8, BUT across the Vlan1 and Vlan2 I can ping ok betwen both Switches (thas is the purpose of Vlans...). Many thanks for make me understand this.. justomparra

Community Member

Re: hel for sw 2940!!

to dnewell24...: I'm testing the switches. In SW2940 nº1 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 7). In SW2940 nº2 I have Vlan1 (port1 to 4) and Vlan2 and (port 5 to 8). The connections are: PC(IP 192.168.242.111)----(Port8, trunk)SW2940 nº1(Port9, trunk)---(fiber)----(port9, trunk)SW2940 nº2(port1 to 4,Vlan1 and port5 to 8,Vlan2)----CODEC video IP with ethernet port and IP 192.168.242.1). Ping from the PC to CODEC is OK in end ports of Vlan 1 BUT no in Vlan2. I was thinking (it was an error)that this is a malfunction of the trunk port8, BUT across the Vlan1 and Vlan2 I can ping ok betwen both Switches (thas is the purpose of Vlans...). Many thanks for make me understand this.. justomparra

Bronze

Re: hel for sw 2940!!

If I understand it correctly, for any inter-VLAN communication you need a device that can route between IP subnet/VLANs.

Your PC is connected to a trunk port. Is trunking configured on the NIC? If not, that would explain your earlier explanation. When using dot1q trunking the switch recognizes untagged frames (frames without any VLAN trunk information) as the native VLAN. If your NIC isn't configured for trunking every frame sent by the PC would be untagged. If your SW2940n1 port 8 is configured with native VLAN 1, your non-trunking PC sending untagged frames would belong to VLAN 1. Therefore this would allow your PC to ping any device, including the IP Codec, in the network on VLAN 1.

Conversely, if you configured port 8 with native VLAN 2 this would assign the PC to VLAN 2. Therefore, allowing your PC to ping every device in VLAN 2.

Your non-trunking PC is unaware of VLANs. The upstream switch assumes any frames that are untagged belong to the native VLAN.

To establish connectivity to both VLANs from the PC add a Layer 3 device or configure 802.1q trunking on the NIC.

HTH= Hope This Helps,

Ryan

Community Member

Re: hel for sw 2940!!

Ryan: Many thanks for this explanation... I'm very satisfied and today I learn more about this..

Best regards..

justomparra

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