RIPng Technology White Paper
Transcript of RIPng Technology White Paper
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RIPng Technology White Paper
Keyword: IPv4, IPv6, RIP, RIPng
Abstract: RIPng was developed from RIP to support IPv6. This document describes the RIPng
implementation, differences between RIPng and RIP, and RIPng application scenarios.
Acronyms:
Acronym Full spelling
CIDR Classless Inter-domain Routing
IGP Interior Gateway Protocol
RIP Routing Information Protocol
RIPng RIP next generation
RTE Route Table Entry
VLSM Variable Length Subnet Mask
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Table of Contents
1 Overview.........................................................................................................................................3 2 RIPng Implementation....................................................................................................................3
2.1 Introduction to RIP ...............................................................................................................3 2.1.1 Mechanism................................................................................................................3 2.1.2 RIP Versions .............................................................................................................4
2.2 Differences Between RIPng and RIP...................................................................................4 2.2.1 Packets......................................................................................................................4 2.2.2 Authentication............................................................................................................6 2.2.3 Compatibility with Network Layer Protocols..............................................................6
3 Application Scenarios.....................................................................................................................7 3.1 Network Diagram.................................................................................................................7 3.2 Network Requirements ........................................................................................................7
4 References .....................................................................................................................................7
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1 Overview
RIP is a distance-vector Interior Gateway Protocol (IGP) developed by the IETF. It iswidely used in small-sized IPv4 networks due to ease of implementation,
configuration and maintenance.
To route IPv6 packets, the IETF developed RIPng based on RIP. RIPng has become
a main routing protocol used on IPv6 networks.
2 RIPng Implementation RIPng works basically the same way as RIP but has some differences from RIP to
support IPv6 address format. The following describes RIP briefly before detailing how
different RIPng and RIP are.
2.1 Introduction to RIP
2.1.1 Mechanism
RIP uses UDP and port 520 to exchange route information.
RIP uses a hop count to measure the distance to a destination. The hop count is
known as a metric. The hop count from a router to a directly connected network is 0.
The hop count from a router to a directly connected router is 1. To limit convergence
time, a RIP metric ranges from 0 to 15. A metric value of 16 (or greater) is considered
infinite, which means the destination network is unreachable.
The following describes how RIP works:
(1) After RIP is enabled, a router sends request messages to neighboring routers,and listens for RIP request or response messages from neighboring routers.
(2) Upon receiving response messages, the router processes the routing update
information in the messages, updates its local routing table, and sends
triggered update messages to its neighbors.
(3) All routers on the network do the same to keep the latest routing information.
By default, a RIP router sends its routing table to neighbors every 30 seconds. RIP
ages out routes by adopting an aging mechanism to keep only valid routes.
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2.1.2 RIP Versions
RIP has two versions: RIPv1 and RIPv2.
RIPv1, a classful routing protocol, supports message advertisement via broadcast
only. RIPv1 protocol messages do not carry mask information, which means it can
only recognize routing information of natural networks such as Classes A, B, and C.
That is why RIPv1 does not support discontiguous subnets.
RIPv2 is a classless routing protocol. Compared with RIPv1, RIPv2 has the following
advantages:
Supporting route tags. Route tags are used in route policies to flexibly control
routes.
Supporting masks, route summarization and Classless Inter-Domain Routing
(CIDR).
Allowing for designating the best next hop on a broadcast network.
Supporting multicast routing update to reduce resource consumption.
Supporting plain text authentication and MD5 authentication by adding an
authentication route table entry (RTE) into updates to enhance security.
2.2 Differences Between RIPng and RIP RIPng works basically the same way as RIP but has the following differences from
RIP to support IPv6:
2.2.1 Packets 1. Different IP address lengths
RIPng uses 128-bit IP addresses, compared with RIPv2's 32-bit addresses.
2. Different packet lengths A RIPv2 message carries up to 25 route entries, while the maximum number of RTEs
in a RIPng packet depends on the IPv6 MTU of the sending interface.
3. Different packet formats Like a RIPv2 packet, a RIPng packet consists of a header and multiple RTEs. The
following figure shows the packet formats of RIP and RIPng:
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Figure 1 RIPv2 packet format (upper) and RIPng packet format (lower)
Different from RIPv2, RIPng has two types of RTEs:
Next hop RTE: Defines the IPv6 address of a next hop.
IPv6 prefix RTE: A next hop RTE can be followed by multiple IPv6 prefix RTEs
that use the same next hop. An IPv6 prefix RTE describes the destination IPv6
address, route tag, prefix length and metric of a RIPng route entry. The following figure shows the format of the next hop RTE. IPv6 next hop address is
the IPv6 address of the next hop.
Figure 2 Next hop RTE format
The following figure shows the format of the IPv6 prefix RTE:
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IPv6 prefix (16 octets)
Route tag Prefix length Metric
0 7 15 31
Figure 3 IPv6 prefix RTE format
IPv6 prefix: Destination IPv6 address prefix Route tag: Route tag Prefix length: Length of the IPv6 address prefix
Metric: Cost of the route 4. Different packet sending modes RIPv2 can be configured to periodically broadcast or multicast routing information,
while RIPng periodically multicasts routing information.
2.2.2 Authentication In RIPng, the authentication RTEs have been removed. RIPng relies on the
authentication mechanism of IPv6 to ensure integrity and validity.
2.2.3 Compatibility with Network Layer Protocols
RIP can run in IP networks and IPX networks, while RIPng can run in IPv6 networks
only.
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3 Application Scenarios 3.1 Network Diagram
Router H
Router I
IPv6 network
School
Router B Router CRouter A
Figure 4 Typical RIPng application scenario
3.2 Network Requirements A school builds an IPv6 network. All routers and hosts in the network running
IPv6.
The school requires a small office network where any two nodes can
communicate with each other and the network devices can automatically adapt
to topology changes.
In this case, RIPng can be used to enable communication between any two
nodes on the network.
4 References RFC 2080: RIPng for IPv6
RFC 2081: RIPng Protocol Applicability Statement
RFC 1058: Routing Information Protocol
RFC 1721: RIP Version 2 Protocol Analysis
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RFC 2082: RIP-2 MD5 Authentication
RFC 2453: RIP Version 2
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No part of this manual may be reproduced or transmitted in any form or by any means without prior written consent of Hangzhou
H3C Technologies Co., Ltd.
The information in this document is subject to change without notice.