© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configuring EIGRP Configuring Advanced EIGRP Options

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v EIGRP Route Summarization: Automatic Purpose: Smaller routing tables, smaller updates Automatic summarization: –On major network boundaries, subnetworks are summarized to a single classful (major) network. –Automatic summarization occurs by default.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v EIGRP Route Summarization: Manual Manual summarization has the following characteristics: Summarization is configurable on a per-interface basis in any router within a network. When summarization is configured on an interface, the router immediately creates a route pointing to null0. –Loop-prevention mechanism When the last specific route of the summary goes away, the summary is deleted. The minimum metric of the specific routes is used as the metric of the summary route.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v no auto-summary (config-router)# Turns off automatic summarization for the EIGRP process Configuring Route Summarization ip summary-address eigrp as-number address mask [admin-distance] (config-if)# Creates a summary address that this interface will generate

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Manually Summarizing EIGRP Routes

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Router C Routing Table RouterC#show ip route Gateway of last resort is not set /16 is variably subnetted, 3 subnets, 2 masks D /16 is a summary, 00:00:04, Null0 D /24 [90/156160] via , 00:00:04, FastEthernet0/0 D /24 [90/ ] via , 00:00:04, Serial0/0/1 C /24 is directly connected, Serial0/0/ /8 is variably subnetted, 3 subnets, 2 masks C /24 is directly connected, Serial0/0/1 C /24 is directly connected, FastEthernet0/0 D /8 is a summary, 00:00:05, Null0 RouterC#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v EIGRP Load Balancing Routes with a metric equal to the minimum metric are installed in the routing table (equal-cost load balancing). There can be up to six entries in the routing table for the same destination: –The number of entries is configurable. –The default is four. –Set to 1 to disable load balancing.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v EIGRP Unequal-Cost Load Balancing variance multiplier Allows the router to include routes with a metric smaller than the multiplier value times the minimum metric route to that destination Router(config-router)#

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Router E chooses router C to get to network Z, because it has lowest FD of 20. With a variance of 2, router E chooses router B to get to network Z ( = 30) < [2 * (FD) = 40]. Router D is never considered to get to network Z (because 25 > 20). Variance Example

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configuring WAN Links EIGRP supports different WAN links: –Point-to-point links –NBMA Multipoint links Point-to-point links EIGRP uses up to 50% of bandwidth by default; this bandwidth utilization can be changed.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Bandwidth Utilization over WAN Interfaces Bandwidth utilization over point-to-point subinterfaces using Frame Relay: –Treats bandwidth as T1 by default –Should manually configure bandwidth as the CIR of the PVC Bandwidth utilization over multipoint Frame Relay, ATM, and ISDN PRI: –EIGRP uses the bandwidth on the physical interface divided by the number of neighbors on that interface to calculate the bandwidth attributed per neighbor.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Bandwidth Utilization over WAN Interfaces (Cont.) Each PVC can have a different CIR, creating an EIGRP packet-pacing problem. Multipoint interfaces: –Convert these to point-to-point configuration or manually configure bandwidth by multiplying the lowest CIR by the number of PVCs.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v EIGRP WAN Configuration: Frame Relay Hub-and-Spoke Topology Configure each virtual Circuit as point-to-point, specify bandwidth = 1/10 of link capacity Increase EIGRP utilization to 50% of actual VC capacity

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Configure lowest CIR virtual circuit as point-to-point, specify bandwidth = CIR. Configure higher CIR virtual circuits as multipoint, combine CIRs. EIGRP WAN Configuration: Hybrid Multipoint

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Summary EIGRP performs automatic network-boundary summarization, but administrators can disable automatic summarization and perform manual route summarization on an interface-by-interface basis. Summarizing routes creates smaller routing tables. Use the no auto-summary command to disable automatic summarization. Use the ip summary-address eigrp command to create a summary address. EIGRP performs equal-cost load balancing by default for up to four paths (up to six paths can be supported). Use the variance command to configure unequal-cost load balancing.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v Summary (Cont.) EIGRP uses up to 50 percent of the bandwidth of an interface by default. Because of the inherent differences in the operational characteristics of WAN links, this default may not be the best option for all WAN links. Use the ip bandwidth-percent eigrp command to configure EIGRP bandwidth use across WAN links.

© 2006 Cisco Systems, Inc. All rights reserved. BSCI v