OSPF v. EIGRP

Question 1

In OSPF, how do you identify Passive Interfaces?

Answer 1

• show ip ospf interfaces brief
• show ip protocol

Question 2

In EIGRP, how do you identify passive interfaces?

Answer 2

show ip protocols

Question 3

In OSPF, how do you set the router ID?

Answer 3

• router ospf 1
  
  • router-id 1.1.1.1

Question 4

In EIGRP, how do you set the router ID?

Answer 4

• router eigrp 10
  
  • eigrp router-id 1.1.1.1

Question 5

What is the difference between OSPF’s process ID and EIGRP’s ASN?

Answer 5

• For OSPF the process ID can be different on different routers
• For EIGRP the ASN must be the same on all routers

Question 6

What is the difference with Router IDs in OSPF vs EIGRP?

Answer 6

In OSPF, the router-id has to be unique. In EIGRP if it isn’t unique the router won’t be able to accept external routes from another EIGRP with the same router ID.

Question 7

What parameters do EIGRP routers need to have in order to become neighbors?

Answer 7

• Same ASN
• Same subnet (for EIGRPv2 only)
• Same K values
• Pass Authentication if configured

Question 8

What is the difference between OSPF Hello and Dead timers vs EIGRP’s Hello and Hold timers?

Answer 8

• OSPF Hello is 10 seconds, EIGRP’s Hello is 5 seconds
• OSPF Dead time is 40 seconds, EIGRP’s Hold time is 15 seconds.

Question 9

In EIGRP, do routers need to match timers in order to become neighbors?

Answer 9

No

Question 10

In OSPF do routers need to match timers to become neighbors?

Answer 10

Yes

Question 11

What are the multicast addresses for EIGRP and OSPF?

Answer 11

• EIGRP is 224.0.0.9
• OSPF is 224.0.0.5 and 224.0.0.6

Question 12

What is the difference in OSPF vs EIGRP of an infinite route?

Answer 12

• OSPF 2²⁴-1
• EIGRP 2³²-1

Question 13

What is the difference in how OSPF determines a metric vs how EIGRP determines a metric?

Answer 13

• OSPF uses Interface Cost
• EIGRP uses Bandwidth and Delay

Question 14

Does OSPF and EIGRP both do Route Poisoning and Split Horizon?

Answer 14

• Both OSPF and EIGRP do Route Poisoning
• Only EIGRP does Split Horizon

Question 15

What parameters do OSPF routers need to match to become neighbors?

Answer 15

• Interfaces in same subnet
• Authentication (if configured)
• Hello and Dead timers must match
• Router IDs must be unique
• Must be in same area
• MTUs must match

Question 16

In eBGP, what is the command to configure a neighbor?

Answer 16

• router bgp 101
  
  • neighbor 168.182.10.2 remote-as 102

Question 17

What is the difference in how the ‘network’ router subcommand is used in EIGRP vs. OSPF?

Answer 17

No difference. They both use wildcard masks.

Question 18

What is the difference in ‘network’ statements between EIGRP for IPv4 and OSPF for IPv4?

Answer 18

• OSPF adds an Area parameter at the end whereas EIGRP does not.
  
  • EIGRP network statement is ‘network 192.168.1.0 0.0.0.255’
  • OSPF network statement is ‘network 192.168.1.0 0.0.0.255 area 0’

Question 19

What is the difference in range of values between EIGRP ASN and OSPF process ID?

Answer 19

No difference, they both use 1 thru 65,535.

Question 20

When does EIGRP and OSPF send route updates?

Answer 20

• EIGRP only sends updates when there has been a topology change
• OSPF sends updates when there has been a topology change
• OSPF ALSO sends updates when an LSA has expired (every 30 minutes)