Misc 2 - RIP and EIGRP Flashcards
1
Q
What is RIP?
A
- Routing Information Protocol
- Distance vector IGP protocol (uses routing-by-rumor)
- Uses hop count as its metric. Doesn’t take into account link bandwidth
- Maximum hop count is 15. Anything more than this is considered unreachable.
- RIP and RIPv2 are used for IPv4, RIPng is used for IPv6
- By default, RIP will allow 4 paths to the same destination into the routing table and load balance between these
2
Q
What messages does RIP use?
A
- Request - To ask RIP enabled routers to send their routing table
- Response - To send the local router’s routing table to neighboring RIP enabled routers
3
Q
How often do RIP enabled routers share their routing table?
A
Every 30 seconds. This can cause congestion in networks with lots of RIP enabled routers.
4
Q
List drawbacks of RIP (v1).
A
- RIP only advertises classful addresses.
- It is also assumed that any address in the class A range (0.0.0.0 - 126.255.255.255) is a /8 and the same with class B and class C addresses. This is because RIP doesn’t include subnet masks in its advertisements.
- Doesn’t support CIDR or VLSM
- Messages are broadcast to 255.255.255.255 so all routers (even non RIP enabled ones)
5
Q
List benefits of RIPv2 over RIP (v1)
A
- Can support CIDR and VLSM so classless addresses can be advertised since RIPv2 includes subnet mask information in its advertisements
- Messages are sent to multicast 224.0.0.9 (only RIP enabled routers)
6
Q
What command do you use to enable RIPv2?
A
- From global config enter ‘router rip’
- It is best practice to then enter ‘version 2’ as this will ensure you are using RIPv2 instead of RIP
- It is also best to use ‘no auto-summary’ to stop RIPv2 from automatically advertising classful networks by default
- You then need to enter the ‘network <network>' command for each network that is configured on an interface that you want RIP to be enabled on. These will always be translated to classful networks (e.g. entering 'network 10.1.2.3' will automatically change to 'network 10.0.0.0').</network>
- RIP will then form adjacencies with other RIP enabled routers connected to these interfaces. It will advertise the prefixes configured on the interfaces. Not the prefixes entered in the ‘network’ command.
7
Q
True or False. RIP will only advertise the prefix of the network that you enter into the ‘network’ command.
A
False. It will advertise the prefix of the interface.
8
Q
True or False. The ‘network’ command used in RIP configuration tells the router what networks to advertise.
A
False. It tells the router which interfaces to enable RIP on.
9
Q
What does the ‘passive-interface’ command in RIP configuration do?
A
- Tells the router to stop sending RIP messages out of a specified interface
- This is done in RIP configuration mode and not interface configuration mode
- This will not stop the prefix configured on the passive interface from being advertised to other routers out of RIP enabled interfaces
- Same command can be used in OSPF to achieve the same outcome
10
Q
True or False. The ‘passive-interface’ command can be used in OSPF and EIGRP.
A
True. It is used for the same reason as when used in RIP.
11
Q
What does the ‘default-information originate’ command do?
A
- Allows a router to share a default route so that other RIP enabled routers can use this as their default route.
- Same command can be used in OSPF to achieve the same outcome
12
Q
What command can you use to find out what routing protocol(s) a router is using?
A
show ip protocols
13
Q
What is EIGRP?
A
- Enhanced Interior Gateway Routing Protocol (formerly Interior Gateway Routing protocol)
- Advanced distance vector routing protocol
- Used to be Cisco proprietary but can now be used in other vendor equipment
- Much faster than RIP in reacting to network changes
- Does not have a maximum hop count
- Sends messages to multicast 224.0.0.10 (only EIGRP enabled routers)
- The only IGP that performs unequal cost load balancing
- As with RIP, EIGRP will allow 4 paths to the same destination into the routing table and load balance between these
- Uses bandwidth of the slowest links + delay of all links to calculate its metric
14
Q
What commands do you use to enable EIGRP?
A
- From global configuration mode enter ‘router eigrp <AS>' The AS number can be any number but it must match between routers that you want to form adjacencies with.</AS>
- It is also best to use ‘no auto-summary’ to stop EIGRP from automatically advertising classful networks by default
- You then need to enter the ‘network <network>' command for each network that is configured on an interface that you want EIGRP to be enabled on. These will always be translated to classful networks unless you specify a wildcard mask (e.g. entering 'network 10.1.2.3' will automatically change to 'network 10.0.0.0').</network>
- EIGRP will then form adjacencies with other EIGRP enabled routers connected to these interfaces. It will advertise the prefixes configured on the interfaces. Not the prefixes entered in the ‘network’ command.
15
Q
What is the function of a wild card mask?
A
- Used in routing protocols like EIGRP and OSPF to match the network command configured to addresses on interfaces so that the routing protocol can be enabled.
- A 0 means that bit in the address must match the wildcard mask
- A 1 means that bit in the address doesn’t have to match the wildcard mask
- Example: A wildcard mask of 0.0.0.15 means that the first 28 bits of the address must match. Any interfaces with addresses on that do match will have EIGRP enabled.
