Which two routing protocols operate over NBMA point-to-multipoint networks without the use of
point-to-point subinterfaces? (Choose two.)
A.
OSPF
B.
EIGRP
C.
RIPv2
D.
RIPv1
E.
IGRP
F.
IS-IS
Explanation:
OSPF over NBMA
For OSPF to run over NBMA you are required to implement the neighbor IP Address but not subinterfaces
Configure an Interface as Point-to-Multipoint, Nonbroadcast (Non-Broadcast Multi-access
NBMA)
To treat the interface as point-to-multipoint when the media does not support broadcast, perform
the following task in interface configuration mode.http://www.cisco.com/en/US/docs/ios/11_3/feature/guide/ospfpmp.html#wp1960
EIGRP over NBMA
NBMA Interfaces (Frame Relay, X.25, ATM)
It is particularly critical to configure nonbroadcast multi-access (NBMA) interfaces correctly,
because otherwise many EIGRP packets may be lost in the switched network. There are three
basic rules:
There are three different scenarios for NBMA interfaces.
http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094063.shtml#nbma
Configuration Commands
no ip split-horizon eigrp
no ip next-hop-self eigrp
RIP over NBMA
Exchange of Routing Information
RIP is normally a broadcast protocol, and in order for RIP routing updates to reach nonbroadcast
networks, you must configure the Cisco IOS software to permit this exchange of routing
information.To control the set of interfaces with which you want to exchange routing updates, you can disable
the sending of routing updates on specified interfaces by configuring the passive-interface router
configuration command. See the discussion on filtering in the “Filter Routing Information” section
in the “Configuring IP Routing Protocol-Independent Features” module.
An offset list is the mechanism for increasing incoming and outgoing metrics to routes learned via
RIP. Optionally, you can limit the offset list with either an access list or an interface. To increase
the value of routing metrics, use the following command in router configuration mode:
Routing protocols use several timers that determine such variables as the frequency of routing
updates, the length of time before a route becomes invalid, and other parameters. You can adjust
these timers to tune routing protocol performance to better suit your internetwork needs. You can
make the following timer adjustments:
http://www.cisco.com/en/US/docs/ios/iproute_rip/configuration/guide/irr_cfg_rip_ps6441_TSD_Pro
ducts_Configuration_Guide_Chapter.html#wp1061185
IS-IS over NBMA
IS-IS can work over an NBMA multipoint network only if the network is configured with a full mesh.
Anything less than a full mesh could cause serious connectivity and routing issues. However, even
if a full mesh is configured, this is no guarantee that a full mesh will exist at all times. A failure in
the underlying switched WAN network or a misconfiguration on one or more routers could break
the full mesh either temporarily or permanently. Therefore, you should avoid NBMA multipoint
configurations for IS-IS networks. Use point-to-point subinterfaces instead.
http://www.ciscopress.com/articles/article.asp?p=31319&seqNum=5
