Routing Technologies Flashcards
What is the routing table priority criteria
- Next hop
- Route specificity
- Administrative distance
- Metric
What is route poisoning
Sets the TTL counter to maxium to get rid of the route
What is split horizon
Doesn’t tell a router about a route it learnt from that router
Why did Cisco create EIGRP when a protocol such as OSPF existing
EIGRP is a far simpler protocol to learn and maintain
All routers in an area have the same…
Topology table
What is the primary method of implementing multiple areas in ospf
To perform route summarisation
What is an ABR
Area border route - connects areas to area 0
What is an ASBR
automonous system boundary router - path out of the system
How does OSPF determine neighbour relationships
- Determine router ID
- Add interfaces to link state database dictated by network command
- Send hello message on chose interface
- Receive hello
- Send reply hello
6, Master/slave relationship determined - DBDs are acknowledge and review
- Neighbours a synchronised
In ospf, how is the route ID determined
Highest active IP address (loopback beats physical)
Better to set manually.
In ospf, how often are hello messages sent on broadcast/p2p networks?
every 10 sec
In ospf, how often are hello messages sent on NBMA networks
every 30 sec
What details are contained in a hello message
i. Router id
ii. Neighbours
iii. Hello and dead timers
iv. Router priority
v. Network mask
vi. DR/BDR ip address
vii. Area ID
viii. Auth password
What 4 details in a hello packet must match in order for OSPF to work.
Hello and dead timers
Network mask
Area ID
Auth password
How are the DR/BDR elected?
Chosen based on higher priority
Can manually set priority but may need to clear ospf process for it to change
What is the broadcast address for DR/BDR
224.0.0.6
Why is it good practice to adjust the reference bandwidth
So OSPF can function in 10Gbps networks
How is the reference BW changed
- Router ospf 1
* Auto-cost reference-bandwidth 10000
What is a passive interface
Stops advertising routes and sending hello messages
What are the two methods of setting a passive interface
Manually select interface and make passive
Make all interfaces passive by default, then enable ospf on interface you want to send hello packets on (cisco preferred as more secured)
What are the default ospf hello/dead timers
10/40
How can the hello timers be changed
ip ospf hello-interval xx
In Multi-area ospf, how are the routes from other ospf areas listed in the routing table.
IA
Why are loopback interfaces used.
Virtual interfaces
can be set for testing, or using a virtual ip
What command makes a loopback appear as a real network to ospf
- Ip ospf network point-to-point
How is a summary route configured
- area 2 range 10.2.0.0 255.255.0.0
What does the default-information originate command do?
Advertises default routes to ospf
In EIGRP, what are the differences between routing table, topology table, and neighbour table.
routing table - the best routes
topology table - closest to link-state DB in ospf, all of the best routes (successor), and 2nd best routes (feasible successor)
neighbour table - formed when neighbours are established
Why would you choose to use EiGRP
- Backup routes (fast convergence/DUAL)
- Simple configuration
- Felxibility im summarisation
- Unequal cost load-balancing
- Combines best of Distance vector and link state ( limited routing info, but backup paths)
In Eigrp, what is the successor and feasible successor
- Describe routes in the topology table
- Successor is primary and goes in routing table
- FS is back up, not in routing table
In eigrp, what are active and passive routes
- Passive is good, all is working
- Active is when problem occurs and is actively trying to find a new route
What is the Advertised Distance (AD)
How far the target is from the routers neighbour
What is the Feasible Distance (FD)
How far the target is from the router
What is the single multicast address that all EIGRP communication is sent to?
224.0.0.10
What are the 5 message types in EIGRP
Hello – forms relationship Update – sends updates Query – asks about routes Reply – response to query Ack – acknowledges the update, query and reply message
What is the EIGRP metric
BW & Delay
What is auto-summary
When routes in the routing table are automatically summarised
How do you stop EIGRP from auto summarisation
No auto-summary
How is EIGRP load balanced
Automatically done if equal cost.
If not equal cost, using the variance command
In eigrp, what are the default hello and hold timers
5 & 15 secs
Hold is always 3 x hello
How do you see EIGRP hello timer for a given interface?
sh ip eigrp interface detail
How can you see the hold timer for eigrp
sh ip eigrp neighbours
How would you adjust the Hello timer for EIGRP running in autonomous system 5 to once every 3 seconds?
ip hello-interval eigrp 5 3
What command turns on ipv6 routing
ipv6 unicast-routing
What characters are put in the middle of a router MAC address in order to auto-generate the last 64 bits of the EUI-64 Link Local address
FFFE
When routing with OSPFv3 or EIGRP for IPv6, why is it important to manually set the router-id
Because there will most likely be no ipv4 address set to automatically set one
How does configuring OSPFv3/EIGRP for IPv6 compare to configuring for IPv4
You no longer use the network command
You enable the protocol then apply it to the interface
How would you turn off OSPFv3
No ipv6 router ospf 1
This also removes the config from the interface
