CCIE Pursuit Blog

April 28, 2008

Internetwork Expert Volume II: Lab 5 – Section 2

Bridging and Switching – 16 Points

2.1 VLAN Assignments

Easy enough task with all four switches running in VTP Transparent mode.  I actually finished all of the Layer 2 tasks (including Frame Relay) and then came back to this task to see which VLANs would need to be added.  The only connection that was not working was r4 (fa0/0 in VLAN4 on sw2) to BB3 (VLAN 4 on sw3).  There was no direct trunk between sw2 and sw3 so I need to add VLAN 4 to sw1:

sw1(config)#vlan 4
sw1(config-vlan)#exit

r4#p 204.12.1.254

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 204.12.1.254, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/4 ms

The IE solution is missing VLAN 2005 on sw1.

2.2 Etherchannel

Easy EtherChannel task.

2.3 Load Distribution

Configure an EtherChannel so that it is optimized for multiple clients behind sw1 reaching a single server behind sw2.

We can use the example cited here:

Load Balancing and Forwarding Methods

port-channel load-balance

We want sw1 (workstations) to use source-based forwarding and sw2 (single server) to use destination-based forwarding.  This will most widely balance our traffic.

dst-ip
 Load distribution is based on the destination host IP address.
 
dst-mac
 Load distribution is based on the destination host MAC address. Packets to the same destination are sent on the same port, but packets to different destinations are sent on different ports in the channel.
 
src-dst-ip
 Load distribution is based on the source and destination host IP address.
 
src-dst-mac
 Load distribution is based on the source and destination host MAC address.
 
src-ip
 Load distribution is based on the source host IP address.
 
src-mac
 Load distribution is based on the source MAC address. Packets from different hosts use different ports in the channel, but packets from the same host use the same port.

Do we want to source on MAC or IP address????

sw2(config)#port-channel load-balance ?
  dst-ip       Dst IP Addr
  dst-mac      Dst Mac Addr
  src-dst-ip   Src XOR Dst IP Addr
  src-dst-mac  Src XOR Dst Mac Addr
  src-ip       Src IP Addr
  src-mac      Src Mac Addr

Task 2.3

For this task traffic from the file server located behind BB2 will be sent across the trunk with the source MAC address of BB2’s Ethernet interface and source IP address of this server. By default all of this traffic would use only one of the Etherchannel trunk links since the default is to load balance based on the source MAC address. With IP address destination based load balancing enabled on SW2 this traffic will now be distributed across both links. Traffic destined to BB2 will have the same source MAC address of R1, the same destination MAC address of BB2 and the same destination IP address, so we need IP address source based load balancing on SW1.

sw1#show etherchannel load-balance
EtherChannel Load-Balancing Operational State (src-ip):
Non-IP: Source MAC address
  IPv4: Source IP address
  IPv6: Source IP address

sw2#show etherchannel load-balance
EtherChannel Load-Balancing Operational State (dst-ip):
Non-IP: Destination MAC address
  IPv4: Destination IP address
  IPv6: Destination IP address

2.4 CAM Table Maintenance

“…configure sw2 so that it discards inactive entries from VLAN 8 and VLAN 88 after 10 seconds.”

mac address-table aging-time

Defaults
The default is 300 seconds.

sw2(config)#mac-address-table aging-time 10 vlan 8
sw2(config)#mac-address-table aging-time 10 vlan 88

sw2#sh mac address-table aging-time
Vlan    Aging Time
—-    ———-
   1     300
  27     300
   4     300
 162     300
   8      10
  88      10

2.5 EtherChannel

Basic layer 3 EtherChannel.  You get to set up an EtherChannel with only one connection.  🙂

 

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