Describing Vlan Qos Packet Flow; Vlan Packet With Priority Routed Out A Fast/Gigabitethernet Interface; Vlan Packet With Priority Routed Out A Serial Interface - Enterasys Security Router X-PeditionTM User Manual

Describing VLAN QoS Packet Flow

The following scenarios illustrate how prioritized VLAN and non-VLAN packets behave across
XSR interfaces with VLAN and QoS configured and include minimal CLI commands.

VLAN Packet with Priority Routed out a Fast/GigabitEthernet Interface

The following scenario is illustrated in
1. After the XSR accepts a VLAN-tagged Ethernet frame, the tag is stripped and the VLAN ID
within the tag is used in the process of mapping the frame to a sub-interface of the Fast/
GigabitEthernet interface. The priority bits are stored internally with the frame.
2. The IP packet in the Ethernet frame is routed according to the XSR's forwarding table which
learns the next hop and outgoing interface.
3. If the outgoing port is associated with a VLAN by a <VLAN ID>, the XSR will create a VLAN
tag with the <VLAN ID> and insert it in the outgoing Ethernet frame. Also, if priority bits are
stored with the frame, they will be marked in the VLAN tag. Lastly, if QoS is configured on
the XSR's output interface, it will be applied accordingly. In this case, the policy map setCos4 is
applied to the output sub-interface FastEthernet 2.1. Since the input priority was 7, it will
match the class matchCos5To7. The output VLAN frame will be marked with a priority of 4.
Ethernet VLAN Tag IP: 9.9.9.1
Priority CFI
Incoming VLAN tagged frame

VLAN Packet with Priority Routed out a Serial Interface

In this scenarios, pictured in
Serial 1. Since the input priority was 7 it will match the class matchCos5To7. The IP packet will be
marked with a DSCP of 46.
Figure
Figure 12-3 VLAN/QoS Ethernet Scenario
IP Routing Table
1.2.3.0/24 F1.1
2
2.2.3.0/24 F2.1
3.3.3.0/24 F2.2
VLAN 1200
9.9.9.0/24 F2.1 (Static)
IP 1.2.3.4/24
F1.1
1
VLAN: 1200
Figure 12-4, the policy map setDscp is applied to the output interface
12-3.
F2.1
Ethernet VLAN Tag IP: 9.9.9.1
F2.2
Priority CFI
VLAN 1400
Outgoing VLAN tagged frame
IP 3.2.3.4/24
Class Map: matchCos5To7
match cos 5 6 7
Policy Map: setCos4
class matchCos5To7
set cos 4
FastEthernet 2.1
service-policy output setCos4
QoS with VLAN
VLAN 1300
IP 2.2.3.4/24
3
VLAN: 1300
XSR User's Guide 12-15