255.255.0 configured 255.255.255.0
dead interval received 40 configured 30
OSPF: hello packet with mismatched E bit
Example 4-7 debug ip ospf packet Command Output
RouterX# ddeebbuugg iipp oossppff ppaacckkeett
OSPF: rcv. v:2 t:1 l:48 rid:200.0.0.116
aid:0.0.0.0 chk:0 aut:2 keyid:1 seq:0x0
154 Chapter 4: Single-Area OSPF Implementation
Table 4-5 describes the signi?¬?cance of the ?¬?elds in this output.
Load Balancing with OSPF
Load balancing is a standard functionality of Cisco IOS Software that is available across all router
platforms. It is inherent to the forwarding process in the router, and it enables a router to use
multiple paths to a destination when it forwards packets. The number of paths used is limited by
the number of entries that the routing protocol puts in the routing table. Four entries is the default
in Cisco IOS Software for IP routing protocols except for BGP. BGP has a default of one entry.
The maximum number of paths you can con?¬?gure is 16.
Figure 4-6 shows an example of con?¬?guring an OSPF router to load balance across six equal-cost
paths.
Table 4-5 debug ip ospf packet Fields
Field Description
v: OSPF version
t: OSPF packet type; possible packet types are as follows:
??? Hello
??? Data description
??? Link-state request
??? Link-state update
??? Link-state acknowledgment
l: OSPF packet length in bytes
rid: OSPF router ID
aid: OSPF area ID
chk: OSPF checksum
aut: OSPF authentication type; possible authentication types are as follows:
0: No authentication
1: Simple password
2: MD5
auk: OSPF authentication key
keyid: MD5 key ID
seq: Sequence number
Introducing OSPF 155
Figure 4-6 OSPF Equal-Cost Load Balancing
The cost (or metric) of an interface in OSPF indicates the overhead that is required to send packets
across a certain interface.
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