EIGRP OSPF BGP

Property

EIGRP

OSPF

BGP

Administrative Distances	Internal - 90	110	EBGP - 20
	External 170		IBGP - 200
Method	Advanced distance vector	Link state	Path vector
Summarization	Auto and manual	Manual	Auto and Manual
VLSM	Yes	Yes	Yes
Convergence Speed	Very fast convergence	Fast	Slow
Timers: Update	Triggered (LAN 5/15, WAN 60/180)	Triggered when network change occurs, send periodic update LSA refreshes every 30 minutes (NBMA 30/120, LAN 10/40)	Triggered (60/180)
(hello/dead)
Network Size	Large	Large	Very large
Mixed-Vendor Devices	No	Yes	Yes
Use multicast	224.0.0.10	224.0.0.5
Feature	- Partial updates conserve network bandwidth	- Minimizes the number of routing table entries	- BGP provides the routing betw these autonomouse systems.
	- Support for IP, AppleTalk, and IPX	- Contains LSA flooding to a reasonable area	- BGP uses the concept of autonomous systems (AS). An autonomous system is a group of networks under a common administration. The Internet Assigned Numbers Authority (IANA) assigns AS numbers: 1 to 64511 are public AS
	- Runs directly over IP, using protocol number 88	- Each routing device takes a copy of the LSA updates its LSDB and forward the LSA to all neighbor devices within area	numbers and 64512 to 65535 are private AS numbers.
	- Support for all Layer2 (data link layer) protocols and topologies	- Minimizes the impact of a topology change	- IGP: A routing protocol that exchanges routing infor within AS. RIP, IGRP, OSPF, IS-IS and EIGRP are examples of IFPs.
	- Load balancing across equal-and unequal-cost pathways	- Enforces the concept of a hierarchical network design	- EGP: A routing protocol that exchanges routing infor betw different AS. BGP is an example of an EGP.
	- Multicast and unicast instead of broadcast address		- The administrative distance for EBGP routes is 20. The administrative distance for IBGP routes is 200.
	- Support for authentication		- BGP neighbors are called peers and must be statically configured.
	- Manual summarization at any interface		- BGP uses TCP port 179. BGP peers exchange incremental, triggered route updates and periodic keepalives.
	- 100% loop-free classless routing
Operation	- IP EIGRP Neighbor Table	Neighbor Table
	- IP EIGRP Topology Table AD+FD	Topology Table LSDB
	- The IP Routing Table	Routing Table
		(LSA-> LSDB-> SPF algorithm-> SPF Tree-> Routing Table)
Function is controlled by	EIGRP’s function is controlled by 4 key technologies:	Following are several types of areas:	BGP uses 3 databases. The first two listed are BGP-specific; the third is shared by all routing processes on the router:
	- Neighbor discovery and maintenance: Periodic hello messages	- Backbone area: Area 0, which is attached to every other area.	- Neighbor database: A list of all configured BGP neighbors. To view it, use the show ip bgp summary
	- The Reliable Transport Protocol (RTP): Controls sending, tracking, and acknowledging EIGRP messages	- Regular area: Nonbackbone area; its database contains both internal and external routes.	command.
	- Diffusing Update Algorithm (DUAL): Determines the best loop-free route	- Stub area: It’s database contains only internal routes and a default route.	- BGP database, or RIB (Routing Information Base): A list of networks known by BGP, along with their
	- Protocol-independent modules (PDM): Modules are “plug-ins” for IP, IPX, Novel Netware and AppleTalk versions of EIGRP	- Totally Stubby Area: Cisco proprietary area designation. Its database contains routes only for its own area and a	paths and attributes. To view it, use the show ip bgp command.
		default route.	- Routing table: A list of the paths to each network used by the router, and the next hop for each network. To view
		- Not-so-stubby area (NSSA): Its database contains internal routes, routes redistributed from a connected routing	it, use the show ip route command.
		process, and optionally a default route.
		- Totally NSSA: Cisco proprietary area designation. Its database contains only routes for its own area, routes redistributed
		from a connected routing process, and a default route.
Packet Types/BGP Message Types	EIGRP uses 5 packet types:	The 5 OSPF packet types follow:	BGP has 4 types of messages:
	- Hello: Identifies neighbors and serves as a keepalive mechanism sent multicast	- Hello: Identifies neighbors and serves as a keepalive.	- Open: After a neighbor is configured, BGP sends an open message to try to establish peering with that neighbor.
	- Update: Reliably sends route information unicast to a specific router	- Link State Request (LSR): Request for a Link State Update (LSU). Contains the type of LSU requested and the	Includes information such as autonomous system number, router ID, and hold time.
	- Query: Reliably requests specific route information query packet multicast to its neighbors	ID of the router requesting it.	- Update: Message used to transfer routing information between peers. Includes new routes, withdrawn routes, and
	- Reply: Reliably responds to a query replies are unicast	- Database Description (DBD): A summary of the LSDB, including the RID and sequence number of each LSA	path attributes.
	- ACK: Acknowledgment	in the LSDB.	- Keepalive: BGP peers exchange keepalive messages every 60 seconds by default. These keep the peering session
		- Link State Update (LSU): Contains a full LSA entry. An LSA includes topology information; for example, the	active.
		RID of this router and the RID and cost to each neighbor. One LSU can contain multiple LSAs.	- Notification: When a problem occurs that causes a router to end the BGP peering session, a notification message
		- Link State Acknowledgment (LSAck): Acknowledges all other OSPF packets (except Hellos).	is sent to the BGP neighbor and the connection is closed.
Neighbor Discovery and Route Exchange	Neighbor Discovery and Route Exchange	Establishing Neighbors and Exchanging Routes	BGP Peering States
	Step 1. Router A sends out a hello.	Step 1. Down state: OSPF process not yet started, so no Hellos sent.	The command show ip bgp neighbors shows a list of peers and the status of their peering session. This status can
	Step 2. Router B sends back a hello and an update. The update contains routing information.	Step 2. Init state: Router sends Hello packets out all OSPF interfaces.	include the following states:
	Step 3. Router A acknowledges the update.	Step 3. Two-way state: Router receives a Hello from another router that contains its own router ID in the neighbor	- Idle: No peering; router is looking for neighbor. Idle (admin) means that the neighbor relationship has been
	Step 4. Router A sends its update.	list. All other required elements match, so routers can become neighbors.	administratively shut down.
	Step 5. Router B acknowledges.	Step 4. Exstart state: If routers become adjacent (exchange routes), they determine which one starts the	- Connect: TCP handshake completed.
		exchange process.	- OpenSent, or Active: An open message was sent to try to establish the peering.
		Step 5. Exchange state: Routers exchange DBDs listing the LSAs in their LSD by RID and sequence number.	- OpenConfirm: Router has received a reply to the open message.
		Step 6. Loading state: Each router compares the DBD received to the contents of its LS database. It then sends a	- Established: Routers have a BGP peering session. This is the desired state.
		LSR for missing or outdated LSAs. Each router responds to its neighbor’s LSR with a Link State Update.
		Each LSU is acknowledged.
		Step 7. Full state: The LSDB has been synchronized with the adjacent neighbor.
Metric (Calculation)	Bandwidth+Delay	Cost= 100 Mbps/Bandwidth	IBGP – 0
			Redistributed routes metric = IGP metric