The Performance Routing - Link Groups feature introduced the ability to define a group of exit links as a preferred set of links, or a fallback set of links for Performance Routing (PfR) to use when optimizing traffic classes specified in a PfR policy.
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Routing Link Groups feature introduced the ability to define a group of exit
links as a preferred set of links, or a fallback set of links for PfR to use
when optimizing traffic classes specified in an PfR policy. PfR currently
selects the best link for a traffic class based on the preferences specified in
a policy and the traffic class performance—using parameters such as
reachability, delay, loss, jitter or MOS—on a path out of the specified link.
Bandwidth utilization, cost, and the range of links can also be considered in
selecting the best link. Link grouping introduces a method of specifying
preferred links for one or more traffic classes in an PfR policy so that the
traffic classes are routed through the best link from a list of preferred
links, referred to as the primary link group. A fallback link group can also be
specified in case there are no links in the primary group that satisfy the
specified policy and performance requirements. If no primary group links are
available, the traffic classes are routed through the best link from the
fallback group. To identify the best exit, PfR probes links from both the
primary and fallback groups.
Primary and fallback
link groups can be configured at the master controller and are identified using
a unique name. Link groups provide a method of grouping links such as high
bandwidth links to be used, for example, by video traffic, by configuring an
PfR policy to specify that the best link is to be selected from the link group
that consists of only high bandwidth links. The traffic classes specified in a
policy can be configured with only one primary link group and one fallback link
group. The priority of a link group can vary between policies, a link group
might be a primary link group for one policy, and a fallback link group for
See the figure below
for an example of how to implement link grouping. Three link groups, ISP1,
ISP2, and ISP3 represent different Internet Service Providers (ISPs) and all
three ISPs have links to interfaces on the three border routers shown in the
figure below. ISP1 links are the most expensive links, but they have the best
Service Level Agreement (SLA) guarantees. ISP3 links are best effort links, and
these links are the cheapest links. ISP2 links are not as good as the ISP1
links, but the ISP2 links are more reliable than the ISP3 links. The cost of
the ISP2 links is higher than the ISP3 links, but lower than ISP1 links. In
this situation, each ISP is created as a link group and associated with an
interface on each border router shown in the figure below.
Figure 1. Link Group
Assuming four types
of traffic class, video, voice, FTP, and data, each traffic class can be routed
through a border router interface belonging to an appropriate link group. Video
and voice traffic classes need the best links so the ISP1 link group is
configured as the primary link group, with ISP2 as the fallback group. FTP
traffic needs reliable links but the cost might be a factor so ISP2 is assigned
as the primary group, and ISP3 is the fallback link group. Note that although
ISP1 provides the most reliable links, it may be too expensive for file
transfer traffic. For data traffic, ISP3 is a good choice as a primary link
group, with ISP2 as the fallback group.
link groups can be used to support spillover. Spillover is when there are two
paths through the network--traffic engineering (TE) tunnels, for example--to
the same provider edge (PE) router, but the tunnels take different paths across
the network and the traffic is sent through one tunnel until it reaches a
traffic load threshold when it spills over to the second tunnel. Using PfR link
groups one tunnel is created as a primary link group and the second tunnel is
the fallback link group. When the first tunnel goes out of policy, PfR switches
to the fallback tunnel link group, which provides the spillover capacity until
the traffic load on the first tunnel drops below the threshold. The tunnels
must be established before the PfR link groups are configured.
Perform this task
on a master controller to set up some performance routing link groups by
identifying an exit link on a border router as a member of a link group, and to
create a PfR map to specify link groups for traffic classes defined in a PfR
policy. In this task, a link group is set up for video traffic and a set of
high bandwidth exit links are identified as members of the video link group
which is identified as a primary link group. A fallback link group is also
A PfR policy is
created using an PfR map where the primary and fall link groups are specified
for traffic classes matching the PfR map criteria. PfR probes both the primary
and fallback group links and selects the best link in the primary link group
for the traffic class specified in this task. If none of the primary links are
within policy, PfR selects the bast link from the fallback group. For more
details about link groups, see the “Performance Routing Link Grouping” section.
border router interface as a PfR-managed external interface.
interfaces are used to forward traffic and for active monitoring.
of two external border router interfaces are required in a PfR-managed network.
At least one external interface must be configured on each border router. A
maximum of 20 external interfaces can be controlled by single master
an interface as a PfR-managed external interface on a router enters PfR border
exit interface configuration mode. In this mode, you can configure maximum link
utilization or cost-based optimization for the interface.
command without the
orinternal keyword places the router in global
configuration mode and not PfR border exit configuration mode. The
no form of this
command should be applied carefully so that active interfaces are not removed
from the router configuration.
PfR border router exit interface as a member of a link group.
link-group-name to specify the link group name for
three link groups can be specified for each interface.
example, the GigabitEthernet 0/0/0 external interface is configured as a member
of the link group named VIDEO.
(PfR) command associates a link group with an interface. Another step, Step 17,
setlink-group (PfR) command to identify the link
group as a primary or fallback group for traffic classes defined in a PfR map.
PfR-managed border exit interface configuration mode and returns to PfR-managed
border router configuration mode.
Repeat Step 5
through Step 7 with appropriate changes to set up link groups for all the
Router(config-pfr-map)# set link-group video fallback voice
link group for traffic classes defined in a PfR map to create a PfR policy.
link-group-name to specify the primary link group
name for the policy.
keyword to specify the fallback link group name for the policy.
example specifies the VIDEO link group as the primary link group for the
traffic class matching the access list ACCESS_VIDEO. The link group VOICE is
specified as the fallback link group.
Exits PfR map configuration mode and returns to privileged EXEC mode.
Router# show pfr master link-group
information about configured PfR link groups.
optionallink-group-nameargument to display information
for the specified PfR link group.
link-group-nameargument is not specified,
information about all PfR link groups is displayed.
example displays information about all configured link groups.
output from the
showpfrmasterlink-group command displays information about
performance routing link groups configured using PfR. In this example, the
VIDEO link group is shown with other configured link groups.
Router# show pfr master link-group
link group video
Border Interface Exit id
192.168.1.2 Gi0/0/0 1
link group voice
Border Interface Exit id
192.168.1.2 Gi0/0/0 1
192.168.1.2 Gi0/0/1 2
192.168.3.2 Gi0/0/3 4
link group data
Border Interface Exit id
192.168.3.2 Gi0/0/2 3
Configuration Examples for Performance Routing Link Groups
Example Implementing Performance Routing Link Groups
The following example shows how to implement link groups. In this example, a PfR map named VIDEO_MAP is created to configure PfR to define a traffic class that matches an access list named ACCESS_VIDEO. The traffic class is configured to use a link group named VIDEO as the primary link group, and a fallback group named VOICE. The VIDEO link group may be a set of high bandwidth links that are preferred for video traffic.
interface GigabitEthernet 0/0/0 external
interface GigabitEthernet 0/0/2 external
interface GigabitEthernet 0/0/1 internal
ip access-list extended ACCESS_VIDEO
permit tcp any 10.1.1.0 0.0.0.255 eq 500
permit tcp any 172.17.1.0 0.0.255.255 eq 500
permit tcp any 172.17.1.0 0.0.255.255 range 700 750
permit tcp 192.168.1.1 0.0.0.0 10.1.2.0 0.0.0.255 eq 800 any any dscp ef
pfr-map VIDEO_MAP 10
match traffic-class access-list ACCESS_VIDEO
set link-group VIDEO fallback VOICE
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Feature Information for Performance Routing Link Groups
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
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Table 1 Feature Information for Performance Routing Link Groups
Performance Routing - Link Groups
Cisco IOS XE Release 3.3S
The Performance Routing - Link Groups feature introduces the ability to define a group of exit links as a preferred set of links, or a fallback set of links for PfR to use when optimizing traffic classes specified in a PfR policy.
The following commands were introduced or modified by this feature: