Configure BEIGRP dynamic routing protocol
Brief introduction of BEIGRP routing protocol
BEIGRP configuration task list
Configure
the sharable percentage of bandwidth
Adjust
the arithmetic coefficient of BEIGRP composite distance
Using
“offset” to adjust the composite distance of the router
Redistribute other routes into the BEIGRP process
Configure
other parameters of BEIGRP
The supervision and maintenance of BEIGRP
Examples of BEIGRP configuration
This chapter will detail the configuration process of BEIGRP dynamic routing protocol.
Brief
introduction of BEIGRP routing protocol
The
technology used by BEIGRP is similar to distance vector routing protocol:
l The
router only makes routing decisions with the information provided by directly
connected neighbours;
l
The router only provides the
routing information it uses to the directly connected neighbors.But,
BEIGRP has some main differences with distance vector routing protocol, which
entitles it to have more advantages:
l
BEIGRP saves all routes from all
neighbours in the topology table, not just the best routes so far;
l
BEIGRP can make query to the
neighbors when it is unable to access the destination and no alternative routes
are available, so, the convergence speed of BEIGRP can compete with the best
link-state protocol.
The
introduction of DUAL----Diffused Update Algorithm is vital for BEIGRP’s
superiority to other traditional distance vector routing protocol. It always
works actively and queries the neighbous when it is unable to access the
destination and there is no alternative routes (feasible replacement). As the
convergence process is active rather than negative (negatively waiting for the
timeout of the routers), so the convergence speed of BEIGRP is very quick.
BEIGRP
is a specific routing protocol designed to adapt to the requirements of EIGRP
and is directly based on IP. It meets the following requirements of BEIGRP:
l
Dynamically discover new neighbor and the disappearance of old neighbors
through “Hello” message;
l
So the transfer of data are all reliable;
l
The transfer protocol permits unicast and multicast data transfer;
l
The transfer protocol itself can adapt to the change of network condition
and neighbor responding;
l
BEIGRP can limit the percentage of its occupation of the bandwidth
according to the requirements
BEIGRP
configuration task list
A
Configure the sharable percentage of bandwidth
Adjust the arithmetic coefficient of BEIGRP composite distance
Using “offset” to
adjust the composite distance of the router
Turn off auto-summary
Customize route summary
Configure other parameters of BEIGRP
The supervision and maintenance of BEIGRP
In
order to create a BEIGRP process, it is required to execute the following
commands:
Step |
Command |
Purpose |
1 |
router beigrp as-number |
Add a BEIGRP process under global
configuration mode |
2 |
network network-number network-mask |
Add addresses to this BEIGRP process
under router configuration mode |
After finishing the above
configuration, BEIGRP will start to run on all interfaces belonging to this
address, discoveres new neighbours through “Hello” and carryes out initial
routing interaction through “update”.
Configure
the sharable percentage of bandwidth
Under
default circumstances, BEIGRP can occupy 50% of the bandwidth at most. You may
wish to change this default value in order to guarantee the normal interaction
of other data, or wishes to adjust the actually usable bandwidth of BEIGRP
through the command when the interface is configured with a bandwidth not fit
for actual situation. Under these
conditions, you can use the following commands under interface configuration
mode:
Command |
Purpose |
ip beigrp bandwidth-percent percent |
Configure the maximum percentage of
BEIGRP messages’ occupation of the bandwidth |
Adjust
the arithmetic coefficient of BEIGRP composite distance
Under
certain situations, the arithmetic co-efficient of BEIGRP composite distance may
need to be adjusted, and finally influences the routing policy of the router.
Although the default arithmetic co-efficient of BEIGRP can satisfy most
networks, but it may still need to be adjusted under some particular conditions.
But this adjust may bring great change to the whole network, so it must be
performed by the most experienced engineers.
Use
the following command under router configuration mode:
Command |
Purpose |
metric weights k1 k2 k3 k4 k5 |
Adjust the arithmetic co-efficient of BEIGRP
composite distance |
Using
“offset” to adjust the composite distance of the router
We
use offset list to purposely add all incoming and outcoming routes according to
the requirement, or the composite distance of certain routes meeting the
requirements. The aim of this approach is to finally influence the routing
result of the router, and meets our expected result. During the process of
configuration, the user can designate access list or application interface in
the offset list selectively and according to your requirements, in order to more
clearly notify which routes to carry out operations to increase offset. Looking
at the following command:
Command |
Purpose |
offset{type number | *} {in | out}
access-list-name offset |
Apply an offset list |
The
auto-summary of BEIGRP is different with other dynamic routing protocols, and it
obeys the following rules:
l
When
a BEIGRP process defines several networks, as long as there is at least one
sub-net of this networks exists in the BEIGRP topology list, it creates the
summary route of the defined network.
l
The
established summary route points to interface Null0, and has the distance as the
minimum distance of all the sub-nets of the network included in the route. The
summary route is also injected into the main IP routing table with the
management distance of 5 (unable to be configured)
l
When
sending update to the neighbors in different main IP network, the sub-nets
summarized by rule1 and rule 2 is cancelled and only a summary route will be
sent.
l
Do
not perform summary towards the sub-nets of any networks not listed in BEIGRP
process definition.
Under
certain network situations, you may wish to report every detailed route to the
neighbor, and you may use the following commands:
Command |
Purpose |
no auto-summary |
Turn off auto-summary of the route |
When
auto-summary cannot meet the requirements, you may configure route summary on
each interface running BEIGRP and designate the destination addresses that need
performing summary. The interfaces configured for summary will not send the
concrete update information of the sub -nets belonging this summary address,
while other interfaces are not affected.
Here,
the summary operation follows the following rules:
l After an interface is configured for summary, it creates the summary route of the defined network as long as this network has at least one sub-net in BEIGRP topology list;
l
The
summary route points to interface Null0, and has the distance as the minimum
distance of all the sub-nets of the network included in the route. The summary
route is also injected into the main IP routing table with the management
distance of 5 (unable to be configured)
l
When
sending route update on the interface configured with summary range, the
concrete route belonging to the summary address will be canceled. The update to
other interfaces are not affected.
Command |
Purpose |
ip beigrp summary-address as-number address mask |
Configure route summary on an interface. |
Redistribute other routes into the BEIGRP process
The
redistribute operation follows the
below rules:
l It isn't have to configure the command "default-metric" when redistribute the static routes and the connected routes. The related parameter(such as: bandwidth, delay, reliability , load and MTU ) is attained from the related interface.
l It isn't necessary to configure the command "default-metric" when redistribute the routes of other beigrp process. The related parameter is attained from the BEIGRP process redistributed.
l It is necessary to configure the command "default-metric" when redistribute the routes of others protocol (such as: rip, ospf). The related parameter is validated by the configuration of "default-metric". If we redistribute the routes of these types without the command "default-metric", the redistribution doesn't work.
In a router running the BEIGRP protocol and the RIP protocol, the following commands must be configured when we need obtain the routes from RIP protocol to BEIGRP protocol.
default-metric bandwidth delay reliability loading mtu |
configure the default parameter of redistribute |
redistribute protocol [process] [route-map name] |
redistribute the routes to BEIGRP protocol. |
Configure
other parameters of BEIGRP
In
order to adapt to different network environments, and to make BEIGRP be more
effectively and fully functions, we may need to adjust the following parameters:
BEIGRP
hello protocol archieves 3 objectives to enable correct BEIGRP operation:
l
It discovers accessible new
neighbors. The discovery is automatic and requires
no manual configuration;
l
It checks neighbors’
configuration and only permits communication with the
neighbours configured with compatible mode.
l
It continues to maintain the
availability of the neighbors and detects the disappearance of the neighbors.
The
router sends “hello” multicast packet on all interfaces running BEIGRP. All
routers support BEIGRP receive these multicast groups, so that it can discover
all neighbours.
“Hello”
protocol uses two timers to detect the disappearance of the neighbours: hello
interval defines the frequency of sending BEIGRP hello messages on the interface
of the router, while hold timer defines the interval of time the router has to
wait for the communication data from the designated neighbor before the
declaration of the neighbour’s death. We ordered that every time it receives
BEIGRP packet from the neighbour router, it resets the hold timer.
Different
network type or network bandwidth will use different default value of hello
timer:
Interface
type encapsulation |
|
Hello
timer (second) |
Hold
timer (second) |
LAN interface |
Any |
5 |
15 |
WAN interface |
HDLC or PPP |
5 |
15 |
NBMA interface, bandwidth<=T1 |
60 |
180 |
|
NBMA interface, bandwidth>T1 |
5 |
15 |
|
The
point-to-point sub-interface of NBMA interface |
5 |
15 |
The
difference of the default value of the timer in Hello protocol may induce the
result that the BEIGRP neighbours connected to different IP sub-network use
different hello and hold timer. To resolve the problem, the hello packet of
every router designates its own hold timer, every BEIGRP router uses
neighbour’s the designated hold timer of the hello group to decide the timeout
of this neighbour. Here, it can enable the appearance of different neighbour
error detection timers in the different stands of the same WAN nephogram. But
under some particular situation, the default value of the timer cannot be met,
so if you want to adjust the time interval of sending hello messages, use the
following command:
Command |
Purpose |
ip beigrp hello-interval seconds |
Adjust the time interval of sending hello
message from this interface |
If you wish to adjust the
timeout timer of the neighbour, use the following command:
Command |
Purpose |
ip beigrp hold-time seconds |
Adjust the timeout death time of the
neighbor |
Commonly, we wish to use split-horizon. It
will prevent the routing information from one interface to be broadcasted back
to the same interface, so as to avoid route loop. But under certain
circumstances, this is not the optimized choice, and then we can use the
following command to disable split-horizon:
Command |
Purpose |
no ip beigrp split-horizon |
Turn off horizontal split |
The
supervision and maintenance of BEIGRP
To clear the neighbourship with
all neighbours, use the following command:
Command |
Purpose |
clear ip beigrp neighbors [as-number | interface]
|
To clear the neighborship with all
neighbours |
In
order to show various statistics information of BEIGRP, execute the following
commands:
Command |
Purpose |
show ip beigrp interfaces [interface] [as-number] |
show interface information |
show ip beigrp neighbors [as-number
| interface] |
show neighbor information |
show ip beigrp topology [as-number | all-link | summary
| active] |
show topology information |
Examples of
BEIGRP configuration
An example of route summary
interface Ethernet 1/1
ip beigrp summary-address 1 10.0.0.0 255.0.0.0
!
router beigrp 1
network 172.16.0.0 255.255.0.0
no auto-summary