In our haste to purchase switches for an already over-run project, it would appear we overlooked the product features of the 3560G.
I have been asked to enabled netflow on one of the two switches we use in a production environment, but after much head scratching - the 3560 doesn't support it.
Looking further into it, the whole 3000 series doesn't. Unless you either buy the uplink 10G modules (but then I'm sure it'll only allow you to monitor uplinks) or use a trimmed down version of netflow exporting (appearinging in 12.2(58)SE) from a later revision firmware. Of course, we are a few releases behind that - but I think it might be worth giving it a go anyway to try and satisfy the request.
So, its a netflow no go. For now.
Showing posts with label flow. Show all posts
Showing posts with label flow. Show all posts
Thursday, 19 July 2012
Tuesday, 17 January 2012
Cisco IP Interface switching
Whilst studying some text on NAT, I kept noticing segements of text referring to Cisco switching mechanisms.
Here's a line of the text:
"On a NAT tranlsation table, an asterix means that the translation is occurring in the fast-switched path. By default the first packet in a NAT translation will always be process-switched" - so whats all this fast/process switched business?
Cisco layer 3 devices have three switching modes, Process Switching, Fast Switching, and Cisco Express Forwarding switching.
If you see the configuration line "'no ip route-cache" on an interface the packets entering the interface will be process switched, which means the CPU will do the switching - a potential burden on a router.
Fast switching overcame the issue by route caching the first packet so that others in the same flow didn't have to hit the CPU - these routes were housed in hardware lookup tables that are independent of the CPU.
CEF (Cisco Express Forwarding) builds on fast switching by using FIB (forwarding information bases) and adjacency tables to quickly link packets/flows with routing table entries and adjacent devices.
This is one way of determining what each interface is doing, have a look for the commands:
*Nothing specified in the interface?*
CEF usually enabled by default - you may see ip cef listed earlier in your config
No ip route-cache
Process switched
ip route-cache
Fast switched
That seems to make a bit more sense.
Here's a line of the text:
"On a NAT tranlsation table, an asterix means that the translation is occurring in the fast-switched path. By default the first packet in a NAT translation will always be process-switched" - so whats all this fast/process switched business?
Cisco layer 3 devices have three switching modes, Process Switching, Fast Switching, and Cisco Express Forwarding switching.
If you see the configuration line "'no ip route-cache" on an interface the packets entering the interface will be process switched, which means the CPU will do the switching - a potential burden on a router.
Fast switching overcame the issue by route caching the first packet so that others in the same flow didn't have to hit the CPU - these routes were housed in hardware lookup tables that are independent of the CPU.
CEF (Cisco Express Forwarding) builds on fast switching by using FIB (forwarding information bases) and adjacency tables to quickly link packets/flows with routing table entries and adjacent devices.
This is one way of determining what each interface is doing, have a look for the commands:
*Nothing specified in the interface?*
CEF usually enabled by default - you may see ip cef listed earlier in your config
No ip route-cache
Process switched
ip route-cache
Fast switched
That seems to make a bit more sense.
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