day 4 Flashcards
route summarization
the ability to take a group of subnetworks and summarize them, as one routing statement entry
reverse route summarization
the ability to take a summarized route and determine what networks a summary covers
default route
gives the router a path to send traffic to destinations that are not in the routing table.
gateway of last resort
the next hop specified in a default route is reffered to as the gateway of last resort.
that next hop will usually be the path out of the internet.
dynamic routing protocols
build routing tables from information received from other routers in the network.
autonomous system (AS)
a group of networks under mutual network administration and sharing a common routing methodology
interior gateway protocol (IGP)
used within an AS to maintain a map for the local topology and adjacant areas
three types of IGP’s
distance-vector, link-state, or hybrid
Exterior Gateway Protocol (EGP)
each AS exchanges reachability information with other ASs using an EGP
Border Gateway Protocol (BGP)
most common exterior gateway protocol
distance-vector routing protocols
advertised as vectors of distance and direction.
the distance metric is usually router hop.
distance vector routing protocols
call for each router to send all or some portion of its routing table only to its neighbors.
EVERYTHING ONLY TO ITS NEIGHBOR
link state routing protocols
routers originate information about themselves, their connected links, and the state of those links.
link state routers only send the state of their routers to other routers
link state routing protocols
link state protocols send only the state of their own links to all routers.
link state algorithms send small updates everywhere.
SMALL UPDATES SENT EVERWHERE
link state routing protocols
OSPF, IS-IS, NLSP
administrative distance
the lower the administrative distance, the more preferred that route will be
administrative distances
connected interface 0 static route 1 external BGP route 20 Internal EIGRP route 90 OSPF route 110 RIP route 120
Routing information protocol version 2 (RIPv2)
distance vector routing protocol that uses hop count as a metric
maximum hop count is 15; 16 is unreachable.
updates RIP to allow VLSM and authentication.
RIP v2 updates are destined for the multicast address 224.0.0.9 using UDP port 520
RIP timers
Route update timer, route invalid timer, route flush timer, hold-down timer
route update timer
sends complete routing table updates to neighbors every 30 seconds
route invalid timer
if router has not heard any updates within the invalid timer period, the route is deemed invalid.
the router will send an update to its neighbors, letting them know the route is invalid
route flush timer
amount of time for a router to remove an invalid route from the routing table
hold-down timer
when changes occur on a route, the route is placed in hold down..no changes are accepted until the hold down timer expires
loop avoidance
Triggered updates, split horizon, route poisoning
triggered updates
triggered updates are sent before the update timer has expired
split horizon
routes that are learned from a neighboring router are not sent back to that neighboring router
route poisoning
route poisining is a method by which RIP shuts down redundant links
show ip route
this command displays the routing table as it currently exists on the router
show ip protocols
identifies other running protocols which are not currently involved in the IP routing process
