Chapter 9
Advanced Routing
Protocols
1
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
2
Classful and Classless Routing Protocols
„ In general, distancevector routing protocols
send periodic updates of
their entire routing table
to their directly connected
neighbors.
3
Classful and Classless Rout. Prot. (cont.)
„ Whereas,
link-state
routing protocols flood
nonperiodic
link-state
advertisement of only
changed
routes
throughout the entire
internetwork.
4
Classful and Classless Rout. Prot. (cont.)
„Routing protocols are also
defined as either classful or
classless,
terms
that
describe how the routing
protocols handles subnet
mask information in its
routing table updates
5
Classful and Classless Rout. Prot. (cont.)
„Classful routing protocols
summarize networks to
their
major
network
boundaries (Class A, B, or
C) and do not carry subnet
mask information to their
routing table updates.
6
Classful and Classless Rout. Prot. (cont.)
„RIPv1 and IGRP are classful
routing protocols; they do
not carry any subnet mask
information in their routing
table
updates.
Fig. 9-1
shows the update message
format for RIPv1.
7
Classful and Classless Rout. Prot. (cont.)
„Fig. 9-2 shows an example of
how different major network
separate two subnets from the
same
major
network,
192.168.12.0/24. This is called
discontiguous subnets.
8
Classful and Classless Rout. Prot. (cont.)
„ Fig. 9-3 shows the
configuration of RIPv1 on
RouterA. This will cause
problems in the network
in this example.
9
Classful and Classless Rout. Prot. (cont.)
„ Fig. 9-4 shows the
routing table of RouterB
after RIPv1 has been
configured
on
just
RouterA and RouterB.
10
Classful and Classless Rout. Prot. (cont.)
„ After configuration of
RouterC
with
RIPv1,
however, RouterB’s routing
table changes quickly.
„ Fig. 9-5 shows the two
equal cost routes in
RouterB’s routing table.
11
Classful and Classless Rout. Prot. (cont.)
„ Fig. 9-6 shows a ping
attempt by RouterB to
192.168.12.33 using the
extended ping command.
12
Classful and Classless Rout. Prot. (cont.)
„As you can see, the ping
work,
but
only
intermittently. This is a
result of the dual equal
cost route in RouterB’s
routing table.
13
Classful and Classless Rout. Prot. (cont.)
„Classful routing protocols
cannot adopt to work in
an environment where
discontiguous networks
or VLSM exist.
14
Classful and Classless Rout. Prot. (cont.)
„Classless routing protocols
can carry subnet mask
information in the routing
table updates.
„RIPv2, EIGRP, OSPF and BGP
are classless routing protocols.
Fig. 9-7 shows RIPv2’s route
update message format.
15
Classful and Classless Rout. Prot. (cont.)
„Converting from RIPv1 to
RIPv2 is very simple. Fig.
9-8 shows the commands
to convert RouterB to
RIPv2.
16
Classful and Classless Rout. Prot. (cont.)
„Fig. 9-9 shows RouterB’s
routing table after the
conversion.
17
Classful and Classless Rout. Prot. (cont.)
„ As a result, the
extended ping command
in Fig. 9-10 works
correctly every time.
18
Classful and Classless Rout. Prot. (cont.)
„ In general, due to the
complexity of modern
networks and the use of
VLSM, most networks
use classless routing
protocols.
19
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
20
RIP version 2
„ RIPv2 is not a totally
new protocol. In reality,
it is a set of extensions
to RIPv1 .
21
RIP version 2 (cont.)
„RIP-1先天的缺陷，例如，收
斂時間過長、只能通過15個
中繼節點、更新通告每30秒
發佈一次消耗網路頻寬及只
考慮中繼節點的數目等問
題，依然存在於RIP-2。
22
RIP version 2 (cont.)
„RIP-2與RIP-1的主要區別
5支援 變動長度子網路遮罩
(VLSM)
5支援認證功能(使用MD5
認證機制)
5更新通告採用Multicast位
址(224.0.0.9)
23
RIP version 2 (cont.)
„ Configuring RIP-2 is a
simple process. Fig. 9-11
shows a simple network in
which two of three routers
are running RIP-2 while a
third router is running RIP-1.
24
RIP version 2 (cont.)
„ Fig. 9-12 shows the
commands necessary to
configure RIPv2 on RouterA.
„ Fig. 9-13 shows that the
current routing protocol is
routing
updates for version 2 are
RIP
and
the
being sent and received.
25
RIP version 2 (cont.)
„
RIPv2
maintains
backward compatibility
with RIPv1.
„ In Fig. 9-11, RouterB
must be configured to
send and receive RIPv1
updates to RouterC.
26
RIP version 2 (cont.)
„ Fig. 9-14 shows a correct
configuration of RouterB to
support RIPv1 and RIPv2.
„ If RouterB had not been
configured to send and
receive version 1 updates,
the errors would be appeared.
(see Fig. 9-15)
27
RIP version 2 (cont.)
„RIPv2 authentication can
occur either by passing
the authentication keys
in clear text or via MD5
authentication.
28
RIP version 2 (cont.)
„RFC 1321 defines MD5 as
an “algorithm that takes
as input a message of
arbitrary
length
and
produces as output 128-bit
‘fingerprint’ or ‘message
digest’ of the input.”
29
RIP version 2 (cont.)
„ In short, using MD5
allows
RIPv2
to
authenticate a routing
peer without sending the
secret key across the link
between the two peer.
30
RIP version 2 (cont.)
„
Fig.
9-16
shows
authentication
being
configured on both RouterA
and RouterB.
31
RIP version 2 (cont.)
„ If authentication only
configured on one of the
two peers, the errors in
Fig.
9-17
would
be
displayed.
32
RIP version 2 (cont.)
„ Fig. 9-18 shows many of
features described in this
section. It shows RouterB
multicasting RIPv2 updates
via 224.0.0.9 to RouterA.
„ In addition, it shows
RouterB broadcasting RIPv1
updates via 255.255.255.255.
33
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
34
EIGRP
„EIGRP (Enhanced IGRP)是
IGRP的加強版，它結合了距
離向量(distance vector)與
連 結 狀 態 (link state) 的 優
點，得以達到快速收斂。
35
EIGRP (cont.)
„ EIGRP也是Cisco 提出的路
由協定(Cisco Proprietary
Protocol) ，具有 距離向量
與連結狀態兩個協定的特
點，又稱為進階的距離向量
協 定 (Advanced Distance
-vector Protocol)。
36
EIGRP (cont.)
„
EIGRP 使 用 DUAL
(Diffusing
Update
Algorithm)演算法，當路徑
發生變化時，DUAL只會傳
送更動的部份，而不是整個
路由表，因此可快速反應。
37
EIGRP (cont.)
„ EIGRP不會 週期性 傳送路由
訊息，因此可以節省頻寬的
使用。
„ 另外，EIGRP也支援 多重的
網 路 層 協 定 ， 例 如 ， IP 、
IPX 及AppleTalk等協定。
38
EIGRP (cont.)
„To make (IGRP to EIGRP)
migration simple, Cisco
created
a feature of
EIGRP called automatic
redistribution.
39
EIGRP (cont.)
„ Both IGRP and EIGRP
have to be configured on
the same router at the
border
between
two
protocols, and they both
use the same AS number.
40
EIGRP (cont.)
„ Fig. 9-19 shows a network
where EIGRP and IGRP
automatic
redistribution
occurs.
„ RouterB is configured with
both EIGRP and IGRP using
the autonomous system
number of 52.
41
EIGRP (cont.)
„ Fig. 9-20 shows the routing
table of RouterA. RouterA
has a normal EIGRP route,
flagged as “D” in the routing
table, and external EIGRP
routes, flagged as “D EX.”
42
EIGRP (cont.)
„ Note that you should use
the following commands
on
RouterB under the
Boson NetSim tool.
router eigrp 52
redistribute igrp 52
network 10.0.0.0
network 172.16.0.0
43
EIGRP (cont.)
„ Note that you should use
the following commands
on
RouterB under the
Boson NetSim tool. (cont.)
router igrp 52
redistribute eigrp 52
network 10.0.0.0
network 172.16.0.0
44
Troubleshooting EIGRP
„ Here are some of main commands
you’ll use when viewing and
troubleshooting EIGRP.
show ip protocols
show ip route
show ip eigrp neighbors
show ip eigrp topology
show ip eigrp traffic
debug ip eigrp
45
Troubleshooting IGRP
„ Here are some of main
commands used to help
troubleshoot IGRP.
show ip protocols
show ip route
debug ip igrp events
debug ip igrp transactions
46
EIGRP (cont.)
„ Cisco developed a entirely
new layer 4 protocol, the
reliable transport protocol
(RTP), for use by EIGRP.
„ RTP provides both reliable
and unreliable delivery. For
example, the Hello packets
are
sent
as
unreliable
multicast.
47
EIGRP (cont.)
„Routing table updates are an
example of an EIGRP packet
type
that
use
reliable
multicast via RTP.
„ Reliable multicast is a
feature of RTP that requires
an ACK via unicast to a
multicast message.
48
EIGRP (cont.)
EIGRP packet type
49
EIGRP (cont.)
„
The
Diffusing
Update
Algorithm (DUAL) is the
heart and soul of EIGRP, and
is the reason that EIGRP can
quickly recover from a link
outage and route around
network problems.
50
EIGRP (cont.)
„ Fig. 9-22 shows the output
of the ‘show ip eigrp
neighbors’ command on
RouterA in Fig. 9-21.
51
EIGRP (cont.)
„ Once neighbors have
been discovered, EIGRP
runs the DUAL algorithm
to create EIGRP topology
table.
52
EIGRP (cont.)
„ Using the ‘show ip eigrp
topology’ command shown
in Fig. 9-23, you can
display
information
garnered from the DUAL
process.
53
EIGRP (cont.)
„EIGRP的運作原理
5在EIGRP網路中，每個 路
由器必須維護鄰近表
(Neighbor Table) 、 拓 樸
表 (Topology Table) 及 路
徑表(Routing Table)等三
種資料。
54
EIGRP (cont.)
„EIGRP的運作原理(續)
5鄰近表(Neighbor Table)
3用來記錄鄰接的路由器
5拓樸表(Topology Table)
3用來記錄所有可到達 目的地
的路徑， 路由器 也依此資料
來建立路徑表。
55
EIGRP (cont.)
„EIGRP的運作原理(續)
5路徑表(Routing Table)
3從拓樸表中，找出可到
達目的地的每條 最佳路
徑 稱之為Successor，
而次佳的路徑稱為
Feasible Successor。
56
EIGRP (cont.)
„EIGRP的運作原理(續)
5路徑表(續)
3請注意，路徑表中只儲
存 Successor ， 而
Feasible Successor則
存放在拓樸表中。
57
EIGRP (cont.)
„EIGRP的運作原理(續)
5在了解前述三個資料表後，
EIGRP的運作，概述如下：
3建立鄰近表
3發現路徑
3選擇路徑
3維護路徑
58
EIGRP (cont.)
„EIGRP的運作原理(續)
3 建 立 鄰 近 表 (Building the
Neighbor Table)
6使用EIGRP的 路由器 會
先傳送Hello packets，
來發現鄰近的 路由器 ，
同時更新路徑。
59
EIGRP (cont.)
„EIGRP的運作原理(續)
3 發 現 路 徑 (Discovering
routes)
6基本上，發現路徑與建立
鄰 近 表 都 是 使 用 Hello
packets同時處理完成的。
60
EIGRP (cont.)
„EIGRP的運作原理(續)
5 在 運 作 的 EIGRP 網 路 中 ，
Hello packets是 週期性地
送出(T1的預設值是5秒，
WAN是60秒)，以確認鄰近
的路由器仍然正常存在。
61
EIGRP (cont.)
ÆEIGRP的運作原理(續)
3 選 擇 路 徑 (Choosing
routes)
6在EIGRP網路中，選擇
路徑是從拓樸表中取出
最佳路徑放入路徑表。
62
EIGRP (cont.)
„EIGRP的運作原理(續)
3選擇路徑(續)
6EIGRP在採用了 頻寬 、 延遲
兩項，作為 最佳路徑 的衡量
指標(cost)。公式如下：
256 [ (10,000,000/最小頻寬) + 延遲總和]
63
EIGRP (cont.)
EIGRP利用頻寬與延遲
計算衡量指標範例一
64
EIGRP (cont.)
範例一說明
5以#1路由器如何找到D網路為
說明對象，分別計算經過#2路
由器與#3路由器的衡量指標。
5利用前述公式算出經過#2路由
器的成本為46,021,376，而經
#3 路 由 器 的 成 本 為
20,307,200。
65
EIGRP (cont.)
範例一說明(續)
5因此#3路由器便為#1路由
器到達D網路的最佳路徑，
並加入於路由表內。
66
EIGRP (cont.)
EIGRP利用頻寬與延遲
計算衡量指標範例二
67
EIGRP (cont.)
„EIGRP的運作原理(續)
3 維 護 路 徑 (Maintaining
routes)
6是指當網路發生變動，如
新的路由器加入、路徑的
cost改變或斷線，此時，
路由器就必須要另尋一條
路徑。
68
EIGRP (cont.)
„EIGRP Configuration
5 EIGRP configuration is
nearly identical to IGRP
configuration. Fig. 9-26
shows the commands
necessary to configure
basic on RouterA.
69
EIGRP (cont.)
„EIGRP Configuration (cont.)
; Fig. 9-27 shows EIGRP
routes in the routing table
of RouterA. All of the EIGRP
routes in this table come
from EIGRP topology table.
70
EIGRP (cont.)
„EIGRP Configuration (cont.)
5 EIGRP supports optional
authentication of routing
peers. However, it only
supports MD5 authentication.
5 Fig.
9-28
shows
the
commands necessary on
RouterA and RouterB to
configure authentication.
71
EIGRP (cont.)
„ To provide robust routing
services on multi-vendor
networks, many system
administrator turn to the
open standards link-state
protocol called OSPF.
72
EIGRP (cont.)
EIGRP & IGRP Similarities
73
EIGRP (cont.)
EIGRP & IGRP Differences
74
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
75
OSPF
„ Open shortest path first
(OSPF)
is
an
open
standards,
link-state
protocol that supports
classless routing, VLSM,
and authentication.
76
OSPF (cont.)
„Each router sends out LSAs
to all routers in an area
describing its attached links.
These LSAs are not periodic.
Instead, they are sent only
when a change occurs in
the network.
77
OSPF (cont.)
„The downside of link-state
protocols comes from the
need for each router hold a
topological database of the
entire area; this requirement
increase CPU and memory
demands on a router.
78
OSPF (cont.)
„ Because OSPF creates an
adjacencies
database,
topological database, and a
routing table, it requires
more memory to run than a
simple protocol such as RIP.
79
OSPF (cont.)
„ Table 9-2 summarizes
the main differences
between distance-vector
and link-state routing
protocols.
80
OSPF (cont.)
„ OSPF is ideally suited for
large networks, as it can
use a concept known as
areas to bound link-state
advertisement.
„An area is the portion of a
network within which LSAs
are connected.
81
OSPF (cont.)
„All OSPF routers configured
with
the
same
areas
identification will accept
LSAs from one another.
„ Fig. 9-29 shows an OSPF
network that has been
designed with two areas.
82
OSPF (cont.)
„In Fig. 9-29, areas 0 LSAs
affect only routers A, B, and
C. LSAs for area 1 only
affect routers B, E, F, and D.
„ Therefore, if a link on
RouterA goes down, it will
inform RouterB and RouterC
that the link has gone down.
83
OSPF (cont.)
„OSPF Concept
5In OSPF, the adjacencies
database
contains
information
about
all
OSPF peer with which a
router has successfully
exchanged Hello packets.
84
OSPF (cont.)
„OSPF Concept (cont.)
5 Once
two neighboring
routers
establish
bidirectional comm. via
Hello packets, they add
one another to their
respective
adjacency
databases.
85
OSPF (cont.)
„OSPF Concept (cont.)
5Hellos are multicast to a
special
multicast
address of 224.0.0.5.
5
On
multi-access
networks
such
as
Ethernet, Hellos are sent
every 10 sec by default.
86
OSPF (cont.)
„OSPF Concept (cont.)
5
On
non-broadcast
networks such as Frame
Relay, Hellos are sent
every 30 seconds by
default.
87
OSPF (cont.)
„OSPF Concept (cont.)
5 OSPF also uses a
topological database,
which
holds
the
common view of the
network formed from
LSAs that are received.
88
OSPF (cont.)
„OSPF Concept (cont.)
5
The
topological
database allows the
routers to run Dijkstra’s
SPF algorithm and find
the best path to a
network.
89
OSPF (cont.)
„OSPF Operation
5OSPF goes through a
series of steps to get a
router up and running.
XThe first thing an OSPF
router does is form
adjacencies
with
neighbors.
90
OSPF (cont.)
„OSPF Operation (cont.)
YThe second thing that
occurs in OSPF is the
election of a DR and
BDR.
91
OSPF (cont.)
„OSPF Operation (cont.)
Z Finally, the routers will
flood their
link-state
advertisements and go
through the process of
selecting the best route
to each network.
92
OSPF (cont.)
„OSPF Operation (cont.)
5 Fig. 9-33 show the
example network that
will be used for the rest
of this chapter.
93
OSPF (cont.)
„OSPF Operation (cont.)
5 Fig. 9-34 displays the
show ip ospf neighbor
command output from
RouterB. It clearly shows
that RouterB has RouterA
and
RouterC
in
its
adjacency database.
94
OSPF (cont.)
Æ補充OSPF的運作原理
5OSPF的運作方式如下：
3建立路由器的相連
3發現路徑
3選擇路徑
3維護路徑資訊
95
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(Establishing
Route Adjacencies)
6藉由Hello協定，建立兩
個 路由器 間連結關係，
並可相互交換連結狀態
訊息。
96
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
6Hello封包是以Multicast
位址(224.0.0.5)方式，傳
送到各個路由器。
97
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒ新加入 路由器 R1時，R1尚
未運作，此時R1開始送出
Hello packet。
98
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒ所有的routers (R2, R3, and
R4)收到此Hello packet後，
會 先 將 R1 納 入Adjacencies
Database ， 再 回 應 Hello
packet給R1。
99
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒR1收到相鄰routers的Hello
packet後，會將這些資訊加
入 自 己 的 Adjacencies
Database。
100
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒ此時R1與R2、R1與R3及
R1 與 R4 都 有 雙 方 的 資
訊，於是建立了雙方的溝
通管道。
101
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
6 選 擇 DR (Designated
Router) 與 BDR (Backup
Designated Router)的主要
目的是，降低 路徑更改的流
量與維護連結狀態的同步。
102
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒ 若 路 由 器 R2 擁 有 較 高 的
priority值，則被選為DR；若
路由器 R4擁有次高的priority
值，則被選為BDR。選完DR
與BDR後，所有的 路由器只能
跟DR與BDR交換資訊。
103
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
ƒ當DR與BDR被選定後，新
加入的路由器就只會跟DR與
BDR交換資訊，而不會與其
他的路由器交換資訊。
104
OSPF (cont.)
ÆOSPF的運作原理(續)
3建立路由器的相連(續)
(註：BDR的主要用途，是
當DR故障時，BDR會
取而代之。)
105
OSPF (cont.)
ÆOSPF的運作原理(續)
3 發 現 路 徑 (Discovering
Route)
nExstart state
oExchange state
pLoading state
qFull state
106
OSPF (cont.)
ÆOSPF的運作原理(續)
3發現路徑(續)
nExstart state:在選定DR
與BDR後，routers就進
入Exstart state，然後向
DR送出Hello封包。
107
OSPF (cont.)
ÆOSPF的運作原理(續)
3發現路徑(續)
oExchange state: DR與
其 他 routers 開 始 進 行 交
換連結狀態資訊。
108
OSPF (cont.)
ÆOSPF的運作原理(續)
3發現路徑(續)
pLoading state: DR與其他
routers在交換 一次 或 多次
的
DD
(Database
Description)封包的過程，
雙 方 皆 會 回 應 LSACK
(Link-state ACK)。
109
OSPF (cont.)
ÆOSPF的運作原理(續)
3發現路徑(續)
q Full state: 當 所 有 的
routers都有相同的 連結
狀態資料庫 時，就處於
Full state。
110
OSPF (cont.)
ÆOSPF的運作原理(續)
3選擇路徑(Choosing Route)
6當所有的routers都就處
於Full state時，緊接著
是建立路徑表。而選擇路
徑就是從臨接路徑表中，
選出最佳路徑。
111
OSPF (cont.)
3選擇路徑(續)
5預設的連線成本計算方式
100,000,000 / 線路頻寬
112
OSPF (cont.)
„Table 9-3 shows Cisco’s
default OSPF costs for
certain link types.
113
OSPF (cont.)
3選擇路徑(續)
Cost = 220
114
OSPF (cont.)
OSPF計算最佳路徑範例
115
OSPF (cont.)
ÆOSPF的運作原理(續)
3維護 路徑資訊 (Maintaining
Routing Information)
6Routers 維護路徑資訊 的
步驟如下：
116
OSPF (cont.)
ÆOSPF的運作原理(續)
3維護路徑資訊(續)
n偵測到網路發生異動的
Router 會 以 Multicast
224.0.0.6 傳送LSU (Link
State Update)封包給DR
與BDR。
117
OSPF (cont.)
ÆOSPF的運作原理(續)
3維護路徑資訊(續)
oDR在收到LSU封包後，
會 利 用 Multicast
224.0.0.5 傳 送 給 其 他 的
routers。
118
OSPF (cont.)
ÆOSPF的運作原理(續)
3維護路徑資訊(續)
p一般的routers收到DR送
來的LSU封包後，若其有
連結到其他網路，則會再
轉送出去。
119
OSPF (cont.)
ÆOSPF的運作原理(續)
3維護路徑資訊(續)
q否則，這些routers會先更
新自己的連結狀態資料庫
(Link State Database) ，
再建立新的路徑表。
120
OSPF (cont.)
„ Single-Area OSPF Configuration
5 The commands to
configure
single-area
OSPF on RouterB are
displayed in Fig. 9-35.
121
OSPF (cont.)
5 Two major commands
are needed for OSPF.
5The first is router ospf
[process
id],
which
turns on OSPF. The
process id is similar to
a process on a OS.
122
OSPF (cont.)
5 The
other
major
command is the network
command.
123
OSPF (cont.)
5 OSPF uses wildcard
masks
in
network
statement.
5Once these two commands
are entered, the router begin
the process of forming
adjacencies and developing
topological database.
124
OSPF (cont.)
ÆWildcard Mask的說明
6 當 Wildcard Mask 的 位 元
為0時，表示don’t care；
當 位 元 為 1 時 ， 表 示 need
match 。 若 此 值 省 略 時 ，
則為預設值0.0.0.0。
125
OSPF (cont.)
ÆWildcard Mask的說明(續)
6範例一：
Source: 203.66.47.1
Source-Wildcard : 0.0.0.255
6屬於203.66.47.0網段的
位址，都符合。
126
OSPF (cont.)
ÆWildcard Mask的說明(續)
6範例二：
Source: 203.66.47.50
Source-Wildcard : 0.0.0.0
6只有203.66.47.50的IP位址
符合。
127
OSPF (cont.)
ÆWildcard Mask的說明(續)
128
OSPF (cont.)
‹ Which of the following
wildcard mask will you use to
match
the
range
180.80.32.0~180.80.63.255?
A. 0.0.0.0
B. 255.255.255.255
D. 0.0.0.255
E. 0.0.255.255
Ans: C
129
OSPF (cont.)
‹ Which IP address and
wildcard mask would you
see
in
the
subnet
202.168.16.43/28?
A. 202.168.16.32 0.0.0.15
B. 202.168.16.32 0.0.0.16
C. 202.168.16.32 0.0.0.7
D. 202.168.16.32 0.0.0.8
Ans: A
130
Interior IP Routing Protocols Compared
131
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
132
Controlling Route Traffic
„ The passive-interface
command is an important
entry-level command for
controlling route traffic.
133
Controlling Route Traffic (cont.)
„ In Fig. 9-37, RouterD may
need to learn of the RIP
routes on the rest of the
network, but the network
does not need to know its
routes because RouterB is
configured to route it
statically.
134
Controlling Route Traffic (cont.)
„In short, you need a way
for RouterD to hear RIP
updates, but not sent out
updates. The passiveinterface
command
allows this.
135
Controlling Route Traffic (cont.)
„ Unfortunately,
this
command disrupts the
functions of EIGRP and
OSPF. The command
causes a router to listen
only on the passive
interface.
136
Contents
ÆClassful and Classless
Routing Protocols
ÆRIP version 2
ÆEIGRP
ÆOSPF
ÆControlling Route Traffic
ÆReview Questions
137
Review Questions
◆ Which three of following
tables will OSPF router
maintain?
a. Routing table
b. Hello table
c. Topological database
d. Adjacencies database
e. Distance-vector table
Ans: a, c, d
138
Review Questions (cont.)
◆ How does OSPF compute
the distance of cost?
a. 106/bandwidth
b. 108/bandwidth
c. bandwidth/108
d. bandwidth/106
e. None of the above
Ans: b
139
Review Questions (cont.)
◆ Which one of the following
multicast addresses will router
use to inform DR when the
network topology changed?
a. 224.0.0.5
b. 224.0.0.6
c. 224.0.0.9
d. 224.0.0.10
e. None of the above
Ans: b
140
Review Questions (cont.)
◆ Which one of the following
multicast address will DR
receive change and flood the
LSU to other routers on the
OSPF network?
a. 224.0.0.5
b. 224.0.0.6
c. 224.0.0.9
d. 224.0.0.10
Ans: a
141
Review Questions (cont.)
◆ Which three of following
routing protocols support
route summarization?
a. RIP
b. IGRP
c. OSPF
d. EIGRP
e. RIP-2
Ans: c, d, e
142
Review Questions (cont.)
◆
Which of the following
protocols is considered to
use link-state logic?
a. RIP
b. IGRP
c. OSPF
d. EIGRP
e. None of the above
Ans: c
143
Review Questions (cont.)
◆
Which of the following
interior protocols support
VLSM?
a. RIP
b. IGRP
c. OSPF
d. EIGRP
Ans: c, d
144
Review Questions (cont.)
Q12: Which of the following
protocols are considered to be
capable of converging quickly?
a. RIP
b. IGRP
c. OSPF
d. EIGRP
Ans: c, d
145
Review Questions (cont.)
◆ What is the maximum entries
number in the routing table
for the same destination of
EIGRP network?
a. 2
b. 4
c. 6
d. 8
e. None of the above
Ans: c
146
Review Questions (cont.)
◆ What is the default entries
number in the routing table
for the same destination of
EIGRP network?
a. 2
b. 4
c. 6
d. 8
e. None of the above
Ans: b
147
Review Questions (cont.)
◆ Which one of the following
multicast addresses is used
by EIGRP?
a. 224.0.0.5
b. 224.0.0.6
c. 224.0.0.9
d. 224.0.0.10
e. None of the above
Ans: d
148
Review Questions (cont.)
◆
Which one of following
routing protocols will you
used to support multiple
routed protocols?
a. RIP
b. IGRP
c. OSPF
d. EIGRP
e. None of the above
Ans: d
149
Review Questions (cont.)
◆ Classless routing protocols
carry _________ in their
routing table?
Ans: subnet mask information
150
Review Questions (cont.)
◆ A backup route in EIGRP
is a(n) _________.
Ans: Feasible Successor
151
Review Questions (cont.)
◆ What command switches
RIP to version 2?
a. router rip 2
b. version 2
c. rip version 2
d. ripv2 on
e. None of the above
Ans: b
152
Review Questions (cont.)
◆ Which type of authentication
send only a hash across a
link
between
two
authentication peers?
a. MD5
b. Clear text
c. Signed secret keys
d. Shared keys
e. None of the above
Ans: a
153
Review Questions (cont.)
◆ What command places the
192.168.12.32/27 network into
OSPF area 0?
a. network 192.168.12.0 area 0
b. network 192.168.12.32 area 0
c. network 192.168.12.0
255.255.255.224 area 0
d. network 192.168.12.32
0.0.0.31 area 0
154
Ans: d
Review Questions (cont.)
◆ What protocol is used by
EIGRP to transport its routing
protocol information?
a. TCP
b. UDP
c. RTP
d. SPX
e. None of the above
Ans: c
155
Review Questions (cont.)
◆ What algorithm is used by
OSPF for path selection?
a. DUAL
b. Open Path First
c. Shortest Path First
d. Default-Information Originate
e. None of the above
Ans: c
156
Review Questions (cont.)
◆ What command displays the
successors
and
feasible
successor for EIGRP?
a. show ip route
b. show ip eigrp topology
c. show running
d. show ip topology
e. None of the above
Ans: b
157
Short Question
‹Which interior IP routing
protocols support VLSM?
Ans: RIP-2, EIGRP, OSPF,
and Integrated IS-IS.
158
Short Question
‹
Which
IP
routing
protocols use distancevector logic?
Ans: RIPv1, RIPv2, and IGRP.
159
Short Question
‹Which interior IP routing
protocols are considered
to converge quickly?
Ans: EIGRP, OSPF,
Integrated IS-IS.
and
160
Short Question
‹List three similarities between
EIGRP’s balanced hybrid logic
and link-state logic.
Ans: XFast convergence
Yneighbor discovery before
sending routing info
Z not sending full updates
on a particular period
161
Short Question
‹ Explain the differences
between full and partial
routing updates.
162
Short Question (cont.)
Ans:
Full
routing
updates
include information about each
subnet during each update
period. Partial updates just
include change routes, such as
newly learned subnets and
subnets whose routes have
failed.
163
Short Question
‹ Define the term balanced
hybrid in relation to the
terms distance vector and
link state.
164
Short Question (cont.)
Ans: Balanced hybrid is a
term used refer to the logic
used by EIGRP. The logic
can be viewed as a
combination of features like
those of distance vector
and link state protocols.
165
Short Question
‹ What is the smallest
summarized
route
that
summarizes the subnets
10.1.63.0, 10.1.64.0, 10.1.70.0,
and 10.1.71.0, all with mask
255.255.255.0?
166
Short Question (cont.)
Ans: Only the first 17 bits of
these
subnets
are
in
common. Therefore, the
smallest
summary
is
10.1.0.0, all with mask
255.255.128.0.
167
Short Question
‹ What is the smallest
summarized
route
that
summarizes the subnets
10.5.111.0,
10.5.112.0,
10.5.113.0, and 10.5.114.0,
all with mask 255.255.255.0?
168
Short Question (cont.)
Ans: The first 19 bits of these
subnets are in common.
Therefore,
the
smallest
summary is 10.5.96.0, all
with mask 255.255.224.0.
169
Short Question
‹ What is the smallest
summarized
route
that
summarizes the subnets
10.5.110.32, 10.5.110.48, and
10.5.110.64, all with mask
255.255.255.248?
170
Short Question (cont.)
Ans: The first 25 bits of these
subnets are in common.
Therefore,
the
smallest
summary is 10.5.110.0, all
with mask 255.255.255.128.
171
Short Question
‹ Of the routing protocols
RIPv1,
RIPv2,
IGRP,
EIGRP, and OSPF, which
are classless ?
Ans: RIPv2, EIGRP and
OSPF.
172
Short Question
‹ Of the routing protocols
RIPv1,
RIPv2,
IGRP,
EIGRP, and OSPF, which
support VLSM ?
Ans: RIPv2, EIGRP and
OSPF.
173