Latest CCNP Routing Interview Questions Part – 5
1.Describe the operation of Anycast RP.
Two or more RPs are configured with the same IP address. The IP addresses of the RPs are advertised using a unicast IP routing protocol. Each multicast router chooses the closet RP. If an RP fails,the routers switch to the next nearest RP after the unicast ip routing protocol converges. The MSDP is used between RPs to exchange active multicast source information.
2.What protocols do switches use to prevent the broadcasting of multicast traffic?
CGMP and IGMP Snooping.
3.Why are the Cisco multicast routing protocols referred to as protocol independent?
Multicast forwarding decisions are based on the entries in the unicast IP routing table. Multicast is not dependent on how the unicast IP routing table was built; you cans use any dynamic interior routing protocol,static routes,or a combination of the two.
4.Why is BGP a better choice for Internet routing than the IGPs?
RIP version 1 and IGRP are classful protocols and do not advertise subnet mask information. RIP version 2 has a limited network diameter of 15 hops. EIGRP,OSPF,and IS-IS use computational intensive algorithms for determining a shortest path.
BGP relies on simple techniques for best path selection and loop detection,and can handle the number of network prefixes required for Internet routing.
5.What is the major difference between BGP and IGP route summarization?
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.
6.Why does IBGP require a full mesh?
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 neighbours will not advertise prefixes learned from one IBGP neighbour to another IBGP neighbour; therefore,a full mesh is required.
7.Name two methods for reducing the number of IBGP connections.
Route reflector and confederation.
8.What is synchronization?
Synchronization is a property of IBGP. An IBGP router will not accept a prefix received from an IBGP neighbour if the prefix is not already in the IP routing table.
9.What is the first thing that BGP checks to determine if a prefix is accessible?
BGP checks the NEXT HOP attribute to determine if the NEXT HOP is accessible or in the IP routing table.
10.Name all the ways for installing a prefix in the BGP routing table.
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 neighbour.
11.What is the order of preference for the BGP attributes AS_PATH,LOCAL_PREF,MED,and WEIGHT?
WEIGHT,LOACL_PREF,AS_PATH,MED
12.What is the purpose of the metric or MULTI_EXIT_DISC attribute?
MED is used to prefer a path into an autonomous system. A lower MED value is preferred.
13.What is the scope of the LOCAL_PREF attribute?
The LOCAL _PREF attribute is advertised throughout the autonomous system.
14.What is the purpose of the LOCAL_PREF attribute?
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).
15.What is the scope of the WEIGHT attribute?
WEIGHT has only local significance and is not advertised to BGP peers.
16.What is the purpose of the WEIGHT attribute?
If a router has more than one route to the same IP prefix,the best path is the one with the highest WEIGHT value.
17.What is the purpose of the AS_PATH attribute?
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).
18.Describe four differences between the operation of IBGP and EBGP.
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 neighbour.
4. EBGP advertises all prefixes learned from an EBGP neighbour to all other EBGP neighbours. IBGP routers do not advertise prefixes learned from one IBGP neighbour to another IBGP neighbour.
19.How many OSPF databases are on an OSPF router?
The number of OSPF databases on a router is equal to the number of OSPF areas configured on the router.
20.What is the administrative distance of OSPF routes?
110
21.If a router learns about the same network prefix through RIP,IGRP,EIGRP,and OSPF,which route will be preferred?
1. EIGRP has an administrative distance of 90
2. IGRP has an administrative distance of 100.
3. OSPF has an administrative distance of 1
4. RIP has an administrative distance of 120.Therefore,the EIGRP route is preferred.
22.Describe the structure and format of an NSAP address.
An NSAP address has a length of8 to 20 bytes and consists of three components:
1. One to 13 byte area id
2. Six byte system id
3. One byte NSAP selector that is always equal to zero for a router
23.Assume a router has a loopback address of 13
5.7
7.
9.25
The loopback address written in dotted decimal and using three digits for each byte has a value of 13
5.07
7.00
9.25
3.50.7
7.00.9
2.5
4.
24.Describe the difference between an OSPF and IS-IS backbone.
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.
25.In IS-IS,what does Level 1 routing mean?
Level 1 routing is routing between destinations in the same IS-IS area.
26.What is the OSPF counterpart to Level l routing?
Intra-area routing.
27.In IS-IS,what is the function of a Level 1-2 router?
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.
28.What is the OSPF counterpart to a Level 1-2 IS-IS router?
An Area Border Router (ABR).
29.What is the difference between the types of routes allowed by default into IS-IS and OSPF areas?
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.
30.What is route leaking?
Redistribution of Level 2 routes into an area as Level l routes.