- Bronze, 100 points or more
Hi every body!
please consider the following scenario
Sw1 is configured to trust cos from ip phone.f2 is layer- 3 interface with ip address 184.108.40.206
sw2 f2 is layer- 3 interface ,ip address 199.199.`199.2
sw1 receives frame from ip phone with cos=5 on f1. It will eventually transmit it on f2 which is layer 3 interface. At egress port f2 which is layer- 3 interface, how would switch find the queue for ip phone frames.Will queues at egress port are mapped against cos value if yes how? being layer 3 interface f2 can not have cos values mapped to queues.
2) let say switch receives a packet 1, and adjacency table has no mac address listing for next hop, p1 is punted where layer 3 engine( route processor) sends the arp request, adjacency table is updated . The question is who forwarded the p1? layer 3 engine or cef having learned the mac address? I understand that any subsequent packets will be cef -switched but who switched the first packet p1 ? is it cef or router processor?
thanks a lot!
My understanding is that first packet is process switched and then CEF switched after that.
1) If the interface is a L3 interface then you would use the DSCP marking to map it to a queue because as you say a CoS value would have no meaning here. So you would have a DSCP to queue mapping within your switch.
2) Not sure exactly what you mean. For the first packet there will be an ARP request and the packet will be then forwarded using the result of that request.
The result of that device will also be used to populate the CEF adjacency table and the next packet will just use that entry rather than having to go to the router processor.