EIGRP - Routing Protocols and Concepts - page 398

Important fields for our discussion include the Opcode field and the Autonomous System (AS) field.
Opcode specifies the EIGRP packet type, which includes

Update

■

Query

■

Reply

■

Hello

■

The number in the AS field is used to track multiple instances of EIGRP.

Encapsulated in the EIGRP packet header is the TLV (Type/Length/Value), shown in Figure 9-3. Fill
in the missing field contents.

Figure 9-3 EIGRP Parameters TLV (Answer)

Data Link Frame
Header

IP Packet
Header

EIGRP Packet
Header

Type/Length/Values Types:
EIGRP Parameters TLV

Bit 0 7 8 15 16 23 24 31

Type = 0x0001 Length

K1
K5

K2 K3 K4

Values

Reserved Hold Time

This EIGRP Parameters message includes the weights that EIGRP uses for its composite metric. By
default, only bandwidth and delay are weighted. Both are equally weighted; therefore, the K1 field
for bandwidth and the K3 field for delay are both set to 1 . The other K values are set to 0 .

The hold time is the amount of time the EIGRP neighbor receiving this message should wait before
considering the advertising router to be down.

Figure 9-4 shows the IP Internal message that is used to advertise EIGRP routes within an
autonomous system. Fill in the missing field contents.

Figure 9-4 IP Internal Routes TLV (Answer)

Data Link Frame
Header

IP Packet
Header

EIGRP Packet
Header

Type/Length/Values Types:
IP Internal Routes TLV

Bit 0 7 8 15 16 23 24 31

Type = 0x0102 Length

Next Hop

Delay
Bandwidth

Values

MTU Hope Count

Reliability Load Reserved

Prefix Length Destination

Important fields include the metric fields ( Delay and Bandwidth ), the subnet mask field ( Prefix
Length ), and the Destination field.

Explain how the delay value is calculated.

Delay is calculated as the sum of delays from source to destination in units of 10 microseconds.