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13 messages in net.nether.puck.cisco-nsp[c-nsp] GSR and 3750 GE-LX link problem| From | Sent On | Attachments |
|---|---|---|
| Yu-lin Chang | Jan 11, 2005 4:28 am | |
| McCallum, Robert | Jan 11, 2005 4:38 am | |
| Joe Shen | Jan 11, 2005 4:49 am | |
| Yu-lin Chang | Jan 11, 2005 5:05 am | |
| Yu-lin Chang | Jan 11, 2005 5:08 am | |
| Joe Shen | Jan 11, 2005 5:36 am | |
| McCallum, Robert | Jan 11, 2005 5:41 am | |
| CEW CEW | Jan 11, 2005 9:16 am | |
| Michael K. Smith | Jan 11, 2005 4:03 pm | |
| Gert Doering | Jan 11, 2005 4:21 pm | |
| Michael K. Smith | Jan 11, 2005 4:23 pm | |
| Gert Doering | Jan 11, 2005 4:27 pm | |
| Michael Smith | Jan 11, 2005 5:48 pm |
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| Subject: | [c-nsp] GSR and 3750 GE-LX link problem | Actions... |
|---|---|---|
| From: | Michael Smith (mksm...@noanet.net) | |
| Date: | Jan 11, 2005 5:48:44 pm | |
| List: | net.nether.puck.cisco-nsp | |
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-----Original Message----- From: Gert Doering [mailto:ge...@greenie.muc.de] Sent: Tuesday, January 11, 2005 1:27 PM To: Michael Smith Cc: Gert Doering; Yu-lin Chang; cisc...@puck.nether.net Subject: Re: [c-nsp] GSR and 3750 GE-LX link problem
Hi,
On Tue, Jan 11, 2005 at 01:23:58PM -0800, Michael K. Smith wrote:
For local ping, this isn't necessary - the routers won't forward packets if "no ip routing" is set, but that's not necessary to ping.
Are you sure? I'm not sure how the 3750 deals with encapsulation without the underlying protocols enabled. Does the ethernet interface encapsulate the traffic as a Layer 3 packet or a Layer 2 frame? Is the encapsulation based solely upon the "no ip switchport" command on the 3750?
"no ip routing" doesn't mean "IP switched off".
It switches off IP *forwarding*, but the box will still do IP pracket processing as a host - no forwarding, no use of routing protocols, use of "ip default-gateway" to decide where to default-route packets (which is also what the boot monitor does when you boot from TFTP).
(I admit that I'm not sure about the 3750, but the basic principle of "no ip routing" vs. "ip routing" is embedded so deeply into IOS that it would surprise me very much if the 3750 is different here).
I *think* there is a difference when configuring the router intelligence on the switching platforms, but I could be wrong. :-) When there is a VLAN interface on the switch and the Gigabit Ethernet port is set to switchport mode, either trunking or no, the frames are forwarded across the Gigabit Ethernet port as Ethernet frames and "terminate" on the VLAN interface. The VLAN interface then has the IP address on the same subnet as the ip default-gateway for local management use.
On the other hand, when the Gigabit Ethernet port is given an IP address and set to "no switchport" the port forwards the traffic as encapsulated IP packets, not Ethernet frames. That's why I wondered about the "ip routing" process being activated on the device. Without it, does the switch still forward the packets? Or, does it forward them as frames? Or, is it an incomplete configuration so it doesn't forward them at all?
I'd love to hear the answer from Cisco on this one just for my own edification.
Mike
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