Network+ Routing Protocols

What is the difference between an interior gateway protocol (IGP) and an exterior gateway protocol (EGP)?

-An IGP routes and operates inside an autonomous system (AS) (a collection of subnets and networks under common administrative control, meaning that routers in a common AS have the same routing table) -An EGP routes and operates between two ASes -IGPs include Routing Information Protocol (RIP), Interior Gateway Routing Protocol (IGRP), Open Shortest Path First (OSPF), and Intermediate System-to-Intermediate System (IS-IS) -EGPs include Border Gateway Protocol (BGP)

What are some characteristics of Border Gateway Protocol (BGP)?

-Default AD for external is 20; for internal, 200 -Routes between two ASes, but can also route within an AS (not as reliable); hence BGP is considered a hybrid protocol -BGP acts like a distance vector protocol; BGP routers broadcast path vectors and hop counts for a different-number AS (this is called an AS path) -BGP works well with VLSMs and very large internetworks like the Internet

What are some characteristics of Enhanced Interior Gateway Routing Protocol (EIGRP)?

-Default AD for internal is 90; for external, 170 -A hybrid protocol that combines distance vector and link state characteristics -An EIGRP router sends distance vector updates to its neighbors like hop count, but an EIGRP router also sends specific updates only when internetwork topology changes -An EIGRP router stores routing info in three tables: neighbor, topology, and routing -A topology table contains an entire map of the internetwork and remote network destinations are mapped to the best path (successor route) and backup paths (feasible successor) -Uses Reliable Transport Protocol (RTP) to transfer packets and Diffusing Update Algorithm (DUAL) to update tables -EIGRP works well with VLSMs and very large internetworks

What are some characteristics of Open Shortest Path First (OSPF)?

-Default AD is 110 -OSPF ensures efficiency by organizing an AS hierarchically, dividing the AS into subnetworks called areas -Areas are linked to each other with area border routers (ABRs), and all areas link back to area 0 (backbone) -ASes are linked together with autonomous system border routers (ASBRs) -OSPF works with both IPv4 and IPv6 addresses, but they are stored on separate tables -OSPF works well with VLSMs and very large internetworks

What are some characteristics of Intermediate System-to-Intermediate System (IS-IS)?

-Default AD is 115 -Works identically to OSPF, but IPv4 and IPv6 addresses are stored in the same table, so ISPs prefer IS-IS over OSPF -In an IS-IS autonomous system, you don't need a backbone area -Systems are divided into L1 and L2 intermediate systems: L1 systems routed within an area, L2 systems route between areas -IS-IS can perform connectionless operations -IS-IS works well with VLSMs and very large internetworks

What are some characteristics of Routing Information Protocol (RIP)?

-Default AD is 120 -A distance vector protocol that comes in two versions: RIPv1 and RIPv2 -RIPv1 works only on classful networks (those whose interfaces have the same subnet mask) while RIPv2 works on classless networks (those whose interfaces may have different subnet masks) and discontiguous networks -A RIP router broadcasts its routing table to its neighbors every 30 seconds or so; maximum hop count is 15 -RIP works best for small networks

What is the difference between distance vector and link state protocols?

-Distance vector protocols use hop count (number of routers a packet must pass through) to assess a route's reliability -Distance vector routers broadcast their routing tables to their neighbors on occasion -Routing information includes network number, exit interface, and hop count to the network -Distance vector protocols are best used for smaller internetworks with a common subnet mask -Link state protocols don't use just hop count but also bandwidth -Link state routers broadcast their tables only when necessary, i.e, when the internetwork topology changes -Link state routers store three tables: routing table, neighbor table, and topology table -Routing information also includes subnet mask of network -Link state protocols are best used for larger internetworks and variable-length subnet masks (VLSMs)

What are first hop redundancy protocols (FHRPs)?

-FHRPs combined multiple physical routers to appear as if there is only one logical router on the network -A virtual router can have virtual IP and MAC addresses and route packets like any other router -One physical router, the active router, acts as the virtual router -If active router fails, a standby router takes over -Active and standby routers use hello packets to communicate with and verify each other -FHRPs include Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP)

What are some methods of tunneling in IPv6?

-General Routing Encapsulation (GRE): Creates a VPN tunnel between two IPv4 hosts over an IPv6 network -6to4 tunneling: An IPv6 packet receives an IPv4 header, allowing it to pass through an IPv4 network. Can be done statically or automatically -Intra-Site Automatic Tunnel Addressing Protocol (ISATAP): An ISATAP server can be placed in the middle of an IPv4 network, and only IPv6 hosts must be configured to connect with it -Teredo: Lets IPv6 packets move through an IPv4 network containing a Network Address Translation (NAT) device by encapsulating IPv6 packets into UDPv4 datagrams and giving packets globally unique IPv6. Clients can connect to a Teredo server

What are some unique IPv6 routing features?

-Router advertisement: Here, an IPv6 host sends a multicast message to a nearby router, asking a router for an IPv6 prefix. The router then sends a network prefix to the host, which the host then uses to autoconfigure its own IPv6 address using EUI-64 -Neighbor discovery: IPv6 hosts recognize each other using link-local addresses (prefix FE80::/64). An IPv6 host sends a multicast message looking for the appropriate link-local address, and another IPv6 host sends a multicast message in response. The two hosts can then communicate with each other

What are some characteristics of Hot Standby Router Protocol (HSRP) and Virtual Router Redundancy Protocol (VRRP)?

-VRRP is the open-standard edition of HSRP; both function identically -HSRP lets you define standby groups, consisting of a virtual router, an active router, and no more than seven standby routers -When the active router fails, a standby router serves as the virtual router -Active and standby HSRP routers use four different timers to communicate with each other -Hello timers let routers verify each others' roles and states in the network -Hold timers let standby routers check if the active router is not working and lets standby routers decide if they should take over -Active timers verify the state of the active router -Standby timers verify the state of the standby routers

List sources of routing information by default administrative distance (AD)

Connected interface: 0 Static route: 1 External BGP: 20 Internal EIGRP: 90 IGRP: 100 OSPF: 110 IS-IS: 115 RIPv1 and RIPv2: 120 External EIGRP: 170 Internal BGP: 200 Unknown route: 255

What the IPv6 versions of some well-known IPv4 routing protocols?

The following protocols all use multicast addresses to communicate with neighbors and link-local addresses to identify neighbors -RIP Next Generation (RIPng): Works just like RIP, but uses multicast messages with prefix FF02::9 to communicate -EIGRPv6: Works just like EIGRP, but uses multicast messages with prefix FF02::A to communicate -OSPFv3: Works just like OSPF, but uses multicast messages with prefixes FF02::5 or FF02::6