Information Technology Reference
In-Depth Information
Classless routing protocols advertise the subnet mask with each route. You can configure
subnetworks of a given IP network number with different subnet masks (VLSM). You can
configure large LANs with a smaller subnet mask and configure serial links with a larger
subnet mask, thereby conserving IP address space. Classless routing protocols also allow
flexible route summarization and supernetting (CIDR). You create supernets by aggregat-
ing classful IP networks. For example, 200.100.100.0/23 is a supernet of 200.100.100.0/24
and 200.100.101.0/24. Classless routing protocols are
RIPv2
■
OSPF
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EIGRP
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IS-IS
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RIPng
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OSPFv3
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EIGRP for IPv6
■
BGP
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IPv4 Versus IPv6 Routing Protocols
With the increasing use of the IPv6 protocol, the CCDA must be prepared to design net-
works using IPv6 routing protocols. As IPv6 was defined, routing protocols needed to be
updated to support the new IP address structure. None of the IPv4 routing protocols sup-
port IPv6 networks, and none of the IPv6 routing protocols are backward compatible with
IPv4 networks. But both protocols can coexist on the same network, each with its own
routing protocol. Devices with dual stacks recognize which protocol is being used by the
IP Version field in the IP header.
RIPng is the IPv6-compatible RIP routing protocol. EIGRP for IPv6 is the new version of
EIGRP that supports IPv6 networks. OSPFv3 was developed for IPv6, and OSPFv2 re-
mains for IPv4. Internet drafts were written to provide IPv6 routing using IS-IS. Multipro-
tocol extensions for BGP provide IPv6 support for BGP. Table 10-4 summarizes IPv4
versus IPv6 routing protocols.
Ta b l e 1 0 - 4
IPv4 and IPv6 Routing Protocols
IPv4 Routing Protocols
IPv6 Routing Protocols
RIPv2
RIPng
EIGRP
EIGRP for IPv6
OSPFv2
OSPFv3
IS-IS
IS-IS for IPv6
BGP
Multiprotocol BGP
