14-3
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 14 Configuring MLS
Understanding How Layer 3 Switching Works
Understanding IP Unicast Rewrite
Received IP unicast packets are (conceptually) formatted as follows:
After the switch rewrites an IP unicast packet, it is (conceptually) formatted as follows:
Understanding IPX Unicast Rewrite
Received IPX packets are (conceptually) formatted as follows:
After the switch rewrites an IPX packet, it is (conceptually) formatted as follows:
Understanding IP Multicast Rewrite
Received IP multicast packets are (conceptually) formatted as follows:
Layer 2 Frame Header
Layer 3 IP Header
Data
FCS
Destination
Source
Destination
Source
TTL
Checksum
MSFC MAC
Source A MAC
Destination B IP
Source A IP
n
calculation1
Layer 2 Frame Header
Layer 3 IP Header
Data FCS
Destination
Source
Destination
Source
TTL Checksum
Destination B MAC
MSFC MAC
Destination B IP
Source A IP n-1
calculation2
Layer 2 Frame Header
Layer 3 IPX Header
Data FCS
Destination
Source
Checksum/
IPX Length/
Transport Control
Destination Net/
Node/
Socket
Source Net/
Node/
Socket
MSFC MAC
Source A MAC
n
Destination B IPX
Source A IPX
Layer 2 Frame Header
Layer 3 IPX Header
Data FCS
Destination
Source
Checksum/
IPX Length/
Transport Control
Destination Net/
Node/
Socket
Source Net/
Node/
Socket
Destination B
MAC
MSFC MAC
n+1
Destination B IPX
Source A IPX
Layer 2 Frame Header
Layer 3 IP Header
Data
FCS
Destination
Source
Destination
Source
TTL
Checksum
Group G1 MAC
1
1.
In this example, Destination B is a member of Group G1.
Source A MAC
Group G1 IP
Source A IP
n
calculation1