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Routing moves a LETTER or telephone call to the ACCESS layer.

Switching makes the final delivery. A switching DECISION is made on the part of the address that is not used in routing.

Routing moves a letter or telephone call to the access layer.

Switching makes the final delivery. A switching decision is made on the part of the address that is not used in routing.

A DEFAULT route is used if there is not a SPECIFIC entry in the ROUTING table for the destination.

A default route is used if there is not a specific entry in the routing table for the destination.

Areas allow the design of a hierarchical network. ROUTES can be summarized or blocked in an AREA to reduce the amount of routing INFORMATION on internal OSPF ROUTERS.

Areas allow the design of a hierarchical network. Routes can be summarized or blocked in an area to reduce the amount of routing information on internal OSPF routers.

The reported DISTANCE to a route that is SENT to another router is the feasible distance on the reporting router. Feasible distance is the reported distance plus the metric between the receiving and reporting ROUTERS. The route with the lowest feasible distance is the SUCCESSOR. Any routes with a reported distance that is less than the feasible distance are feasible successors.

The reported distance to a route that is sent to another router is the feasible distance on the reporting router. Feasible distance is the reported distance plus the metric between the receiving and reporting routers. The route with the lowest feasible distance is the successor. Any routes with a reported distance that is less than the feasible distance are feasible successors.

The passive state MEANS that a ROUTER has a successor for a route. The active state means that a router does not have a successor or feasible successor for a route and is actively sending queries to neighbors to GET information about the route.

The passive state means that a router has a successor for a route. The active state means that a router does not have a successor or feasible successor for a route and is actively sending queries to neighbors to get information about the route.

Classless routing PROTOCOLS ADVERTISE subnet mask information along with the NETWORK prefixes. Classful routing protocols do not. Therefore, for a c1assful protocol, all subnets for the major network number being USED must be the same length. Also, c1assful protocol cannot support discontiguous networks prefixes.

Classless routing protocols advertise subnet mask information along with the network prefixes. Classful routing protocols do not. Therefore, for a c1assful protocol, all subnets for the major network number being used must be the same length. Also, c1assful protocol cannot support discontiguous networks prefixes.

FF02:0000:0000:0000:0000:0000: 130F:0005 

FF02:0000:0000:0000:0000:0000: 130F:0005 

64 because 2 bits are needed for the hosts on the NETWORK, LEAVING 6 bits for the subnet.

64 because 2 bits are needed for the hosts on the network, leaving 6 bits for the subnet.

172.16.53.97 through 172.16.53.126.

172.16.53.97 through 172.16.53.126.

OSPF DATABASES on routers in the same area must be identical. If route summarization was allowed WITHIN an area, some routers would have SPECIFIC routes and some routers would have SUMMARY routes for routers in the area. If this were allowed, the databases for the area would never AGREE.

OSPF databases on routers in the same area must be identical. If route summarization was allowed within an area, some routers would have specific routes and some routers would have summary routes for routers in the area. If this were allowed, the databases for the area would never agree.

By default, the cost of an OSPF interface is 1 OO,OOO,OOO/(Interface Bandwidth). The constant 100,000,000 can be CHANGED using the auto-cost reference-bandwidth command.

By default, the cost of an OSPF interface is 1 OO,OOO,OOO/(Interface Bandwidth). The constant 100,000,000 can be changed using the auto-cost reference-bandwidth command.

To connect a nonzero area to the BACKBONE if the nonzero area BECOMES DISCONNECTED from the backbone. A VIRTUAL LINK can also be used if the backbone, or area 0, becomes discontiguous.

To connect a nonzero area to the backbone if the nonzero area becomes disconnected from the backbone. A virtual link can also be used if the backbone, or area 0, becomes discontiguous.

• First, calculate the shortest PATH to an ABR.
• SECOND, calculate the shortest path across AREA 0 to an ABR that is attached to the DESTINATION area.
• Third, calculate the shortest path across the destination area from the ABR to the destination NETWORK.

The router with the HIGHEST interface priority will be the router ID. If all the interface PRIORITIES on the multi-access network are the same, the router with the highest router ID will be the DR.

The router with the highest interface priority will be the router ID. If all the interface priorities on the multi-access network are the same, the router with the highest router ID will be the DR.

If physical interfaces are only used, the OSPF ROUTER id is the highest IP address assigned to an active physical interface. If LOOPBACK interfaces are used, the OSPF router ID is the highest IP address assigned to a loopback interface. If the router-id command is used with the OSPF configuration, the address used with this command will be the router id.

If physical interfaces are only used, the OSPF router id is the highest IP address assigned to an active physical interface. If loopback interfaces are used, the OSPF router ID is the highest IP address assigned to a loopback interface. If the router-id command is used with the OSPF configuration, the address used with this command will be the router id.

OSPF routes are SUMMARIZED on an ABR. EXTERNAL routes are summarized on an ASBR.

OSPF routes are summarized on an ABR. External routes are summarized on an ASBR.

Intra-area, INTER area, EL, E2, Nl, and N2.

Intra-area, inter area, El, E2, Nl, and N2.

ABR, INTERNAL ROUTER, and ASBR.

ABR, internal router, and ASBR.

An El route contains the OSPF COST to reach the ASBR PLUS the cost from the ASBR to the external route. An E2 route contains only the cost from the ASBR to the external route.

An El route contains the OSPF cost to reach the ASBR plus the cost from the ASBR to the external route. An E2 route contains only the cost from the ASBR to the external route.

OSPF intra-area routes and a DEFAULT route. External routes from ABRS are blocked, and external routes from ASBRS are converted to Nl or N2 routes.

OSPF intra-area routes and a default route. External routes from ABRs are blocked, and external routes from ASBRs are converted to Nl or N2 routes.

OSPF intra-area and inter area routes, and possibly a DEFAULT route. EXTERNAL routes from ABRs are blocked, and external routes from ASBRS are converted to Nl or N2 routes.

OSPF intra-area and inter area routes, and possibly a default route. External routes from ABRs are blocked, and external routes from ASBRs are converted to Nl or N2 routes.

OSPF intra-AREA routes and a default ROUTE. OSPF INTER area and EXTERNAL routes are not advertised into a TOTALLY stubby area.

OSPF intra-area routes and a default route. OSPF inter area and external routes are not advertised into a totally stubby area.

OSPF intra-area and inter area ROUTES, and a DEFAULT ROUTE. External routes are not ADVERTISED into a stub area.

OSPF intra-area and inter area routes, and a default route. External routes are not advertised into a stub area.

A narrow METRIC uses 6 bits for the interface metric and 10 bits for the PATH metric. A WIDE metric uses 24 bits for the interface metric and 32 bits for the path metric.

A narrow metric uses 6 bits for the interface metric and 10 bits for the path metric. A wide metric uses 24 bits for the interface metric and 32 bits for the path metric.

An OSPF interface metric is DETERMINED from the interface bandwidth. By default, all IS¬-IS interface metrics are EQUAL to 10. Therefore, the EIGRP ROUTE is preferred.

An OSPF interface metric is determined from the interface bandwidth. By default, all IS¬-IS interface metrics are equal to 10. Therefore, the EIGRP route is preferred.

REDISTRIBUTION of Level 2 ROUTES into an area as Level l routes.

Redistribution of Level 2 routes into an area as Level l routes.

By default, all ROUTES are advertised into all OSPF areas. This includes INTER area OSPF routes and EXTERNAL routes that have been injected into OSPF. By default, IS-IS does not advertise inter area or external routes into an area, but injects a default route.

By default, all routes are advertised into all OSPF areas. This includes inter area OSPF routes and external routes that have been injected into OSPF. By default, IS-IS does not advertise inter area or external routes into an area, but injects a default route.

An AREA BORDER ROUTER (ABR).

An Area Border Router (ABR).

A LEVEL 1-2 router has two IS-IS databases. The Level L database is used for routing to destinations within the router's configured AREA. The Level 2 database is used to route between destinations in different areas.

A Level 1-2 router has two IS-IS databases. The Level l database is used for routing to destinations within the router's configured area. The Level 2 database is used to route between destinations in different areas.

Intra-area ROUTING.

Intra-area routing.

LEVEL 1 ROUTING is routing between DESTINATIONS in the same IS-IS AREA.

Level 1 routing is routing between destinations in the same IS-IS area.

OSPF has a backbone area or area O. All nonzero AREAS must be connected to the backbone through a router or a VIRTUAL LINK. IS-IS has a backbone area MADE up ofa contiguous CHAIN of Level 2 capable routers.

OSPF has a backbone area or area O. All nonzero areas must be connected to the backbone through a router or a virtual link. IS-IS has a backbone area made up ofa contiguous chain of Level 2 capable routers.

An NSAP ADDRESS has a length OF8 to 20 bytes and CONSISTS of three components:

One to 13 byte area ID

Six byte system id

One byte NSAP selector that is always equal to zero for a router

An NSAP address has a length of8 to 20 bytes and consists of three components:

One to 13 byte area id

Six byte system id

One byte NSAP selector that is always equal to zero for a router

• EIGRP has an ADMINISTRATIVE distance of 90
• IGRP has an administrative distance of 100.
• OSPF has an administrative distance of 110.
• RIP has an administrative distance of 120.
• Therefore, the EIGRP route is PREFERRED.

110

110

The number of OSPF DATABASES on a ROUTER is equal to the number of OSPF AREAS configured on the router.

The number of OSPF databases on a router is equal to the number of OSPF areas configured on the router.

1. IBGP is the protocol used between routers in the same autonomous system. EBGP is the protocol used between routers in different autonomous SYSTEMS.
2. IBGP routes must be synchronized before they can be transferred to the IP routing table (unless synchronization is DISABLED).
3. EBGP sets the next HOP attribute to the IP address of the interface used to communicate with the EBGP peer. The next hop attribute is not modified when an IBGProuter advertises a prefix to an IBGP peer if the prefix was LEARNED from an EBGP neighbor.
4. EBGP advertises all prefixes learned from an EBGP neighbor to all other EBGP neighbors. IBGP routers do not ADVERTISE prefixes learned from one IBGP neighbor to another IBGP neighbor

If a router has more than ONE ROUTE to the same IP prefix, the best PATH is the one with the shortest AS _PATH (assuming other BGP attributes are EQUAL).

If a router has more than one route to the same IP prefix, the best path is the one with the shortest AS _PATH (assuming other BGP attributes are equal).

If a router has more than ONE route to the same IP prefix, the BEST PATH is the one with the highest WEIGHT value.

If a router has more than one route to the same IP prefix, the best path is the one with the highest WEIGHT value.

WEIGHT has only LOCAL significance and is not advertised to BGP PEERS.

WEIGHT has only local significance and is not advertised to BGP peers.

If a ROUTER has more than one route to the same IP PREFIX, the best path is the one with the highest LOCAL_PREF (ASSUMING the WEIGHT ATTRIBUTE for the routes is equal).

If a router has more than one route to the same IP prefix, the best path is the one with the highest LOCAL_PREF (assuming the WEIGHT attribute for the routes is equal).

The LOCAL _PREF ATTRIBUTE is advertised throughout the AUTONOMOUS SYSTEM.

The LOCAL _PREF attribute is advertised throughout the autonomous system.

MED is used to prefer a path into an autonomous SYSTEM. A lower MED VALUE is preferred.

MED is used to prefer a path into an autonomous system. A lower MED value is preferred.

WEIGHT, LOACL_PREF, AS_PATH, MED

WEIGHT, LOACL_PREF, AS_PATH, MED

1. Using the network command to transfer a router from the IP ROUTING table to the BGP routing table.
2. Redistributing routes from the IP routing table to the BGP routing table .
3. LEARNED from a BGP neighbor.

BGP checks the NEXT HOP ATTRIBUTE to DETERMINE if the NEXT HOP is ACCESSIBLE or in the IP routing table.

BGP checks the NEXT HOP attribute to determine if the NEXT HOP is accessible or in the IP routing table.

Synchronization is a PROPERTY of IBGP. An IBGP router will not ACCEPT a prefix received from an IBGP NEIGHBOR if the prefix is not already in the IP ROUTING table.

Synchronization is a property of IBGP. An IBGP router will not accept a prefix received from an IBGP neighbor if the prefix is not already in the IP routing table.

ROUTE REFLECTOR and CONFEDERATION.

Route reflector and confederation.

BGP USES the AS _PATH attribute for loop detection. If a router SEES its own AS number in a BGP advertisement, the advertisement is dropped. IBGP routers have the same AS number so the AS number cannot be used for loop detection. IBGP neighbors will not ADVERTISE prefixes learned from one IBGP NEIGHBOR to another IBGP neighbor; therefore, a full mesh is required.

BGP uses the AS _PATH attribute for loop detection. If a router sees its own AS number in a BGP advertisement, the advertisement is dropped. IBGP routers have the same AS number so the AS number cannot be used for loop detection. IBGP neighbors will not advertise prefixes learned from one IBGP neighbor to another IBGP neighbor; therefore, a full mesh is required.

When a summary address is created with an IGP (EIGRP, OSPF, and IS-IS), the specific ROUTES of the summary are not advertised. BGP ADVERTISES the summary, and all the specific routes of the summary UNLESS they are specifically SUPPRESSED.

When a summary address is created with an IGP (EIGRP, OSPF, and IS-IS), the specific routes of the summary are not advertised. BGP advertises the summary, and all the specific routes of the summary unless they are specifically suppressed.