EIGRP - Routing Protocols and Concepts - page 399

Explain how the bandwidth value is determined.

Bandwidth is the lowest configured bandwidth of any interface along the route.

The subnet mask is specified as the prefix length or the number of network bits in the subnet mask.
For example, the subnet mask 255.255.255.0 has a prefix length of 24 .

Figure 9-5 shows the IP External message that is used when external routes are imported into the
EIGRP routing process. Notice that the bottom half of the IP External TLV includes all the fields used
by the IP Internal TLV. Fill in the missing field contents.

Figure 9-5 IP External Routes TLV (Answer)

Data Link Frame
Header

IP Packet
Header

EIGRP Packet
Header

Type/Length/Values Types:
IP External Routes TLV

Bit 0 7 8 15 16 23 24 31

Type = 0x0103 Length

Next Hop

Value
fields
used to
track
external
source of
route.

Originating Routers
Originating Autonomous System Number
Arbitrary Tag

External Protocol Metric

Values Reserved Ext. Protocol ID Flags

Delay
Bandwidth

Same
value
fields used
in the IP
Internal
TLV.

MTU Hope Count

Reliability Load Reserved

Prefix Length Destination

Protocol-Dependent Modules (PDM)

EIGRP has the capability to route several different protocols, including IP, IPX , and AppleTalk , using
protocol-dependent modules (PDM).

RTP

Reliable Transport Protocol (RTP) is the protocol used by EIGRP for the delivery and reception of
EIGRP packets. EIGRP was designed as a network layer independent routing protocol; therefore, RTP
includes both reliable delivery and unreliable delivery of EIGRP packets, similar to TCP and UDP ,
respectively. Reliable RTP requires an acknowledgment to be returned by the receiver to the sender.
An unreliable RTP packet does not require an acknowledgment .

RTP can send packets either as a unicast or a multicast. Multicast EIGRP packets use the reserved
multicast address of 224.0.0.10 .

EIGRP Packet Types

EIGRP relies on different types of packets to maintain its tables and establish relationships with
neighbor routers. Complete the missing elements below by filling in appropriate words or phrases.
When encountered, circle whether the packet is reliable or unreliable and whether it is unicast or multicast.

Hello packets:

(Reliable/ unreliable ) (unicast/ multicast ) sent to the address 224.0.0.10 to discover and maintain
neighbors; contains the router's neighbor table

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