Configuring and Verifying EIGRP
Use the router eigrp and network commands to create an EIGRP routing process. Note that EIGRP requires an autonomous system (AS) number. The AS number does not have to be registered as is the case when routing on the Internet with the Border Gateway Protocol (BGP) routing protocol. However, all routers within an AS must use the same AS number to exchange routing information with each other. Figure 5-3 shows the EIGRP configuration of a simple network.
Figure 5-3 EIGRP Configuration
Autonomous System = 100
172.16.1.0
Autonomous System = 100
172.16.1.1 10.1.1.1 10.1.1.2 10.2.2.2 10.2.2.3 192.168.1.1
192.168.1.0
172.16.1.1 10.1.1.1 10.1.1.2 10.2.2.2 10.2.2.3 192.168.1.1
router eigrp 100 network 172.16.0.0
router eigrp 100 network 192.168.1.0
network 10.0.0.0
network 10.0.0.0
router eigrp 100
network 10.0.0.0
The network command defines a major network number to which the router is directly connected. The EIGRP routing process looks for interfaces that have an IP address that belongs to the networks that are specified with the network command and begins the EIGRP process on these interfaces.
|
Command |
Description |
|
router eigrp 100 |
Enables the EIGRP routing process for AS 100 |
|
network 172.16.0.0 |
Associates network 172.16.0.0 with the EIGRP routing process |
|
network 10.0.0.0 |
Associates network 10.0.0.0 with the EIGRP routing process |
EIGRP sends updates out of the interfaces in networks 10.0.0.0 and 172.16.0.0. The updates include information about networks 10.0.0.0 and 172.16.0.0 and any other networks that EIGRP learns.
EIGRP sends updates out of the interfaces in networks 10.0.0.0 and 172.16.0.0. The updates include information about networks 10.0.0.0 and 172.16.0.0 and any other networks that EIGRP learns.
EIGRP automatically summarizes routes at the classful boundary. In some cases, you might not want automatic summarization to occur. For example, if you have discontiguous networks, you need to disable automatic summarization to minimize router confusion. Figure 5-4 shows an example of how this summarization can cause advertisements for the 172.16.0.0 network to be sent from both Router A and Router B to Router C.
Figure 5-4 Autosummarization Causing Discontinuous Subnets
172.16.5.0 255.255.255.0
192.168.14.16 255.255.255.240
172.16.6.0 255.255.255.0
Figure 5-4 Autosummarization Causing Discontinuous Subnets
172.16.5.0 255.255.255.0
192.168.14.16 255.255.255.240
172.16.6.0 255.255.255.0
To disable automatic summarization, use the no auto-summary command in the EIGRP router configuration mode. When this command is used, both Router A and Router B will advertise the route specific to the subnet of a given interface, as shown in Figure 5-5.
Figure 5-5 Disabling Autosummarization Corrects Problem
172.16.5.0 255.255.255.0
192.168.14.16 255.255.255.240
Figure 5-5 Disabling Autosummarization Corrects Problem
172.16.5.0 255.255.255.0
172.16.6.0 255.255.255.0
192.168.14.16 255.255.255.240
172.16.6.0 255.255.255.0
After you enable EIGRP, various commands can be used to display information about how the protocol is operating. The show ip route eigrp command displays the current EIGRP entries in the routing table.
The show ip protocols command displays the parameters and current state of the active routing protocol process. This command shows the EIGRP AS number. It also displays filtering and redistribution numbers and neighbor and distance information. This also shows the networks that are currently being advertised on the router by the protocol.
Use the show ip eigrp interfaces [type number] [as-number] command to determine on which interfaces EIGRP is active, and to learn information about EIGRP that relates to those interfaces. If you specify an interface by using the type number option, only that interface is displayed. Otherwise, all interfaces on which EIGRP is running are displayed. If you specify an AS using the as-number option, only the routing process for the specified AS is displayed. Otherwise, all EIGRP processes are displayed. Example 5-1 shows the output of the show ip eigrp interfaces command.
Example 5-1 Determining Router Interface EIGRP Status/Information
RouterX# show ip eigrp interfaces
IP EIGRP interfaces for process 109
RouterX# show ip eigrp interfaces
IP EIGRP interfaces for process 109
|
Xmit Queue |
Mean |
Pacing Time |
Multicast |
Pending |
||
|
Interface |
Peers |
Un/Reliable |
SRTT |
Un/Reliable |
Flow Timer |
Routes |
|
Di0 |
0 |
0/0 |
0 |
11/434 |
0 |
0 |
|
Et0 |
1 |
0/0 |
337 |
0/10 |
0 |
0 |
|
SE0:1.16 |
1 |
0/0 |
10 |
1/63 |
103 |
0 |
|
Tu0 |
1 |
0/0 |
330 |
0/16 |
0 |
0 |
|
Field |
Description |
|
Interface |
Interface over which EIGRP is configured |
|
Peers |
Number of directly connected EIGRP neighbors on the interface |
|
Xmit Queue Un/Reliable |
Number of packets remaining in the Unreliable and Reliable queues |
|
Mean SRTT |
Average smoothed round-trip time (SRTT) interval (in milliseconds) for all neighbors on the interface |
|
Pacing Time Un/Reliable |
Number of milliseconds to wait after transmitting unreliable and reliable packets |
|
Multicast Flow Timer |
Number of milliseconds to wait for acknowledgment of a multicast packet by all neighbors before transmitting the next multicast packet |
|
Pending Routes |
Number of routes in the packets in the transmit queue waiting to be sent |
Use the show ip eigrp neighbors command to display the neighbors that were discovered by EIGRP and to determine when neighbors become active and inactive, as demonstrated in Example 5-2. This command is also useful for debugging certain types of transport problems.
Example 5-2 Displaying Discovered Active/Inactive EIGRP Neighbors
RouterX# show ip eigrp neighbors
IP-EIGRP Neighbors for process 77
RouterX# show ip eigrp neighbors
IP-EIGRP Neighbors for process 77
|
Address |
Interface |
Holdtime |
Uptime |
Q |
Seq |
SRTT |
RTO |
|
|
(secs) |
(h:m:s) |
Count |
Num |
(ms) |
(ms) |
|||
|
172.16.81 |
.28 |
Ethernet1 |
13 |
0:00:41 |
0 |
11 |
4 |
20 |
|
172.16.80 |
.28 |
Ethernet0 |
14 |
0:02:01 |
0 |
10 |
12 |
24 |
|
172.16.80 |
.31 |
Ethernet0 |
12 |
0:02:02 |
0 |
4 |
5 |
20 |
|
Field |
Description |
|
process 77 |
AS number that is specified with the router command. |
|
Address |
IP address of the EIGRP peer. |
|
Interface |
Interface on which the router is receiving hello packets from the peer. |
|
Holdtime |
Length of time (in seconds) that Cisco IOS Software waits to hear from the peer before declaring it down. If the peer is using the default hold time, this number is less than 15. If the peer configures a nondefault hold time, the nondefault hold time is displayed. The hold time would be less than 180 on a sub-T1 multipoint interface. |
|
Uptime |
Elapsed time (in hours:minutes:seconds) since the local router first heard from this neighbor. |
|
Q Count |
Number of EIGRP packets (update, query, and reply) that the software is waiting to send. |
|
Seq Num |
Sequence number of the last update, query, or reply packet that was received from this neighbor. |
|
SRTT |
Smooth round-trip time (SRTT). The number of milliseconds that is required for an EIGRP packet to be sent to this neighbor and for the local router to receive an acknowledgment of that packet. |
|
RTO |
Retransmission timeout (RTO) (in milliseconds). This is the amount of time the software waits before resending a packet from the retransmission queue to a neighbor. |
The show ip eigrp topology command displays the EIGRP topology table, the active or passive state of routes, the number of successors, and the feasible distance to the destination, as demonstrated in Example 5-3.
Example 5-3 Displaying EIGRP Topology Information
|
RouterX# |
show ip eigrp topology |
|||
|
IP-EIGRP |
Topology Table for |
process 77 |
||
|
Codes |
P |
- Passive, A - Active, U - Update, Q - Query, R - Reply, |
||
|
r |
- Reply status |
|||
|
P 172 |
16 |
90.0 |
255.255.255.0 |
, 2 successors, FD is 46251776 |
|
via |
172.16.80.28 |
(46251776/46226176), Ethernet0 |
||
|
via |
172.16.81.28 |
(46251776/46226176), Ethernet1 |
||
|
via |
172.16.80.31 |
(46277376/46251776), Serial0 |
||
|
P 172 |
16 |
81.0 |
255.255.255.0 |
, 2 successors, FD is 307200 |
|
via |
Connected, Ethernet1 |
|||
|
via |
172.16.81.28 |
(307200/281600), Ethernet1 |
||
|
via |
172.16.80.28 |
(307200/281600), Ethernet0 |
||
|
via |
172.16.80.31 |
(332800/307200), Serial0 |
||
|
Field |
Description |
|
Codes |
The state of this topology table entry. Passive and Active refer to the EIGRP state with respect to this destination; Update, Query, and Reply refer to the type of packet that is being sent. |
|
P - Passive |
Indicates that no EIGRP computations are being performed for this destination. |
|
A - Active |
Indicates that EIGRP computations are being performed for this destination. |
|
U - Update |
Indicates that an update packet was sent to this destination. |
|
Q - Query |
Indicates that a query packet was sent to this destination. |
|
R - Reply |
Indicates that a reply packet was sent to this destination. |
|
r - Reply status |
A flag that is set after the software has sent a query and is waiting for a reply. |
|
172.16.90.0 |
Destination IP network number. |
|
255.255.255.0 |
Destination subnet mask. |
|
successors |
Number of successors. This number corresponds to the number of next hops in the IP routing table. If "successors" is capitalized, the route or next hop is in a transition state. |
|
FD |
Feasible distance. The feasible distance is the best metric to reach the destination or the best metric that was known when the route went active. This value is used in the feasibility condition check. If the reported distance of the router (the metric after the slash) is less than the feasible distance, the feasibility condition is met and that path is a feasible successor. After the software determines it has a feasible successor, it does not need to send a query for that destination. |
|
replies |
The number of replies that are still outstanding (have not been received) with respect to this destination. This information appears only when the destination is in active state. |
|
state |
The exact EIGRP state that this destination is in. It can be the number 0, 1, 2, or 3. This information appears only when the destination is in the active state. |
|
via |
The IP address of the peer that told the software about this destination. The first n of these entries, where n is the number of successors, are the current successors. The remaining entries on the list are feasible successors. |
|
(46251776/ 46226176) |
The first number is the EIGRP metric that represents the cost to the destination. The second number is the EIGRP metric that this peer advertised. |
|
EthernetO |
The interface from which this information was learned. |
|
Serial0 |
The interface from which this information was learned. |
The show ip eigrp traffic command displays the number of packets sent and received, as demonstrated in Example 5-4.
Example 5-4 Displaying the Number of EIGRP Sent/Received Packets
RouterX# show ip eigrp traffic
IP-EIGRP Traffic Statistics for process 77 Hellos sent/received: 218/205 Updates sent/received: 7/23 Queries sent/received: 2/0 Replies sent/received: 0/2 Acks sent/received: 21/14
|
Field |
Description |
|
process 77 |
The AS number that is specified in the router command |
|
Hellos sent/received |
The number of hello packets that were sent and received |
|
Updates sent/received |
The number of update packets that were sent and received |
|
Queries sent/received |
The number of query packets that were sent and received |
|
Replies sent/received |
The number of reply packets that were sent and received |
|
Acks sent/received |
The number of acknowledgment packets that were sent and received |
The debug ip eigrp privileged EXEC command helps you analyze the EIGRP packets that an interface sends and receives, as demonstrated in Example 5-5. Because the debug ip eigrp command generates a substantial amount of output, use it only when traffic on the network is light.
Example 5-5 Analyzing Sent/Received EIGRP Packets RouterX# debug ip eigrp
IP-EIGRP: Processing incoming UPDATE packet
IP-EIGRP: Ext 192.168.3.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 -256000 104960
IP-EIGRP: Ext 192.168.0.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 -256000 104960
IP-EIGRP: Ext 192.168.3.0 255.255.255.0 M 386560 - 256000 130560 SM 360960 -256000 104960
IP-EIGRP: 172.69.43.0 255.255.255.0, - do advertise out Ethernet0/1 IP-EIGRP: Ext 172.69.43.0 255.255.255.0 metric 371200 - 256000 115200 IP-EIGRP: 192.135.246.0 255.255.255.0, - do advertise out Ethernet0/1 IP-EIGRP: Ext 192.135.246.0 255.255.255.0 metric 46310656 - 45714176 596480 IP-EIGRP: 172.69.40.0 255.255.255.0, - do advertise out Ethernet0/1
Example 5-5 Analyzing Sent/Received EIGRP Packets (Continued)
IP-EIGRP: Ext 172.69.40.0 255.255.255.0 metric 2272256 - 1657856 614400
IP-EIGRP: 192.135.245.0 255.255.255.0, - do advertise out Ethernet0/1
IP-EIGRP: Ext 192.135.245.0 255.255.255.0 metric 40622080 - 40000000 622080
IP-EIGRP: 192.135.244.0 255.255.255.0, - do advertise out Ethernet0/1
|
Field |
Description |
|
IP-EIGRP |
Indicates that this is an IP EIGRP packet. |
|
Ext |
Indicates that the following address is an external destination rather than an internal destination, which would be labeled as Int. |
|
do not advertise out |
Indicates interfaces out which EIGRP will not advertise the given route. This configuration prevents routing loops (split horizon). |
|
M |
Displays the computed metric, which includes the sent metric (SM) and the cost between this router and the neighbor. The first number is the composite metric. The next two numbers are the inverse bandwidth and the delay, respectively. |
|
SM |
Displays the metric as reported by the neighbor. |
Continue reading here: Load Balancing with EIGRP
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