Cisco Switch to 3com Switch

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Hello, Iam having a problem recieving Ip addresses for any device connected to my 3com switch. The 3com switch is connected to a cisco 500 catalyst express switch, which is connected to a cisco 2815 ISR. The ISR is configured as the DHCP server. Im using a crossover cable between the two switches. The switchport on the 500e was configured using the switches device manager utility to connect to another switch using smartport. Anything connected directly to the 3com will not pull an IP. Ive tried configuring a static IP for a device which was connected, still no go. I am still unable to ping anything connected to the cisco switch including my router. Any help would be appreciated.
ASKED: August 16, 2006  5:36 AM
UPDATED: February 3, 2010  2:38 PM

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Did you set up switches with auto-detect for link connection?
Auto-detect between two different vendors may not work as you expect. Try setting both switchports manually.

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  • Norwood
    What if you plug a client into the 500 series switch and bypass the 3Com one. Can you pull an address then? If so, then we know the problem is the 3Com switch not talking to the 500 series switch. It would rule out the router. Have you tried connecting the 3Com switch to a port on the Cisco switch using a crossover cable using a port that's configured just like a client port and not like an uplink one?
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  • Astronomer
    I assume both of the switches are managed. Have you configured IP addresses for both switches? Are you getting link lights on both switches? Do clients on the cisco switch work fine? Can you ping the cisco switch from the 3com switch? This will help narrow down where the problem is. If the problem is the connection between the switches, check the duplex and speed settings on both ports to make sure they match. If these devices are fairly new, they should autonegotiate, but we had to hard code our connections to 100-full to ensure reliable connections. I don't know what smartport does but I suggest turning off any services that might impede any traffic until connectivity is debugged. Does the 3com do auto MDI/MDI-X sensing? If so, you shouldn't need a crossover cable. Are you sure the crossover cable is correctly wired? Are any VLANs configured? Partially configured VLANs can really confuse connectivity issues. Once you can ping the other switch and the router from the 3com then you can try attaching clients to the 3com and check client connectivity to the router. If this doesn't work, give the client a static IP and ping the 3com and work your way toward the router. Again, VLANs can be a problem here. rt
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  • DesertNomad
    Hi all, Thanks for the responses. It seemed there was a problem with the auto negotiation of link connection between the two switches. I took your advice and manually configured the ports for 100/full, tested and it appears to be working fine now. I was able to pull an IP and ping my router and other devices attached to the cisco switch from the 3com. Thanks again for the help.
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  • Edwardzeng
    Are you setting any vlan in the Cisco switch? or Trunking with the gateway(the cisco Router)? and ip helper-address enable ? Try to debuge the packet from the pc and see what will happen? If there is not feed back from the DHCPS server, and just try to Tcpdump or capture the pacet from the gateway, if you set up different vlan in the 3com or cisco switch.
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  • Ahmed0144788747
    hi i have 3 com switch and cisco switch and 2 NDs and core switch the connection like that: core connect to the 2 NDs first ND1 connect to cisco switch second ND2 connect to 3com switch every switch connect to 2 pcs (ND1---pc1) (ND2---pc2) ND1 (vlan1 by default and vlan 172) nd2 (vlan1 by default and vlan 172) pc1 connect to vlan 1 (cisco sw) pc2 connect to vlan 172 (3com sw) but when i connect the pc1 to vlan 172 (cisco switch )the network with other switch fail (cant see it and it cant connect to any thing is there is any problem with connecting cisco with 3com ???
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