routing john kristoff - depaul university · c is lowest path cost in tent, place c in path, exame...
TRANSCRIPT
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
1
Net
wor
k P
roto
cols
Rou
ting
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
2
IP r
outin
g
�
Per
form
ed b
y ro
uter
s
�
Tab
le (
info
rmat
ion
base
) dr
iven
�
For
war
ding
dec
isio
n on
a h
op-b
y-ho
p ba
sis
�
Rou
te d
eter
min
ed b
y de
stin
atio
n IP
add
ress
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
3
Bas
ic IP
forw
ardi
ng p
roce
ss
�
For
an
IP d
atag
ram
rec
eive
d on
an
inte
rfac
e
�
Rem
ove
laye
r 2
info
rmat
ion
�
Ext
ract
des
tinat
ion
IP a
ddre
ss (D
)
�
Fin
d be
st m
atch
for
(D)
in th
e ro
utin
g ta
ble
�
Ext
ract
fow
ardi
ng a
ddre
ss (F
) fo
r ne
xt h
op
�
Cre
ate
laye
r 2
info
rmat
ion
�
Sen
d da
tagr
am to
(F
)
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
4
IP r
outin
g ta
bles
Sin
ce e
ach
entr
y in
a r
outin
g ta
ble
repr
esen
ts
an IP
net
wor
k, th
e si
ze o
f the
rou
ting
tabl
e is
pr
opor
tiona
l to
the
num
ber
of IP
net
wor
ks
know
n th
roug
hout
the
entir
e in
tern
etw
ork.
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
5
IP r
outin
g ta
ble
illus
trat
ed
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
6
Gen
erat
ing
rout
ing
tabl
es
�
Man
ually
�
Sim
ple
for
smal
l, si
ngle
pat
h ne
twor
ks
�
Doe
s no
t sca
le w
ell
�
Use
ful f
or p
erm
anen
t rou
te e
ntrie
s
�
Dyn
amic
ally
�
Allo
ws
quic
k re
-rou
ting
arou
nd fa
iled
node
s/lin
ks
�
Use
ful f
or la
rge
mul
ti-pa
th n
etw
orks
�
Cat
astr
ophi
c, d
istr
ibut
ed fa
ilure
s ar
e po
ssib
le
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
7
IP r
outin
g ill
ustr
ated
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
8
IP r
outin
g ill
ustr
ated
(co
ntin
ued)
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
9
Rou
ting
met
rics
�
Sho
rtes
t/lon
gest
hop
pat
h
�
Low
est/h
ighe
st c
ost p
ath
�
Low
est/h
ighe
st r
elia
bilit
y
�
Bes
t/wor
st la
tenc
y
�
Pol
icy
deci
sion
s
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
10
Som
e te
rmin
olog
y
�
Aut
onom
ous
syst
em (
AS
)
�
A n
etw
ork
or s
et o
f net
wor
ks th
at is
ad
min
istr
ated
by
a si
ngle
ent
ity
�
Inte
rior
gate
way
pro
toco
ls (
IGP
)
�
Rou
ting
prot
ocol
use
d w
ithin
an
AS
�
Ext
erio
r ga
tew
ay p
roto
cols
(E
GP
)
�
Rou
ting
prot
ocol
use
d be
twee
n A
Ses
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
11
Dis
tanc
e ve
ctor
rou
ting
�
Eac
h no
de m
aint
ains
dis
tanc
e to
des
tinat
ion
�
e.g.
4 h
ops
to n
etw
ork
XY
Z, 2
hop
s to
AB
C
�
Per
iodi
cally
adv
ertis
e at
tach
ed n
etw
orks
out
ea
ch li
nk
�
Lear
n fr
om o
ther
rou
ter
adve
rtis
emen
ts
�
Adv
ertis
e le
arne
d ro
utes
�
Als
o kn
own
as B
ellm
an-F
ord
afte
r in
vent
ors
of th
e al
gorit
hm
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
12
Dis
tanc
e ve
ctor
illu
stra
ted
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
13
Dis
tanc
e ve
ctor
illu
stra
ted
(con
tinue
d)
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
14
Dis
tanc
e ve
ctor
illu
stra
ted
(con
verg
ed)
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
15
Pro
blem
s w
ith d
ista
nce
vect
or
�
Con
verg
ence
tim
e ca
n be
slo
w
�
Als
o kn
own
as th
e co
unt t
o in
finity
pro
blem
�
Wha
t hap
pens
whe
n lin
k to
A fa
ils?
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
16
Sol
ving
cou
nt to
infin
ity
�
Hol
d do
wn
�
Adv
ertis
e in
finity
for
rout
e an
d w
ait a
per
iod
of
time
befo
re s
witc
hing
rou
tes.
Hop
e th
at n
ews
of
the
dow
ned
link
will
spr
ead
fast
eno
ugh.
Klu
dge.
�
Rep
ort t
he e
ntire
pat
h
�
Gua
rant
ees
no lo
ops,
but
exp
ensi
ve.
�
Spl
it ho
rizon
�
Do
not a
dver
tise
rout
e to
a n
eigh
bor
if yo
u re
ceiv
ed r
oute
from
that
nei
ghbo
r. N
ot fo
olpr
oof.
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
17
Oth
er d
ista
nce
vect
or
impr
ovem
ents
�
Trig
gere
d up
date
s
�
Adv
ertis
e ch
ange
s im
med
iate
ly.
May
cau
se
rout
e fla
ppin
g, b
ut g
ener
ally
a g
ood
thin
g to
do.
�
Poi
son
reve
rse
�
Use
d w
ith s
plit
horiz
on, a
dver
tise
infin
ity r
athe
r th
an n
othi
ng a
t all.
�
DU
AL
�
Som
ewha
t lik
e ho
ld d
own.
Can
sw
itch
path
s if
new
dis
tanc
e is
low
er.
Suf
ficie
ntly
com
plex
.
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
18
Rou
ting
info
rmat
ion
prot
ocol
(R
IP)
�
Sta
ndar
dize
d in
RF
C 1
058
and
2453
�
The
late
r de
fines
RIP
v2 fo
r im
prov
emen
ts
�
Ver
y si
mpl
e
�
Slo
w c
onve
rgen
ce ti
me
�
UD
P b
road
cast
eve
ry 3
0 se
cond
s (d
efau
lt)
�
Rou
te ti
mes
out
afte
r 18
0 se
cond
s (d
efau
lt)
�
Wid
ely
used
as
an IG
P (
RIP
v2 p
artic
ular
y)
�
15 h
op li
mit
(any
gre
ater
equ
als
infin
ity)
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
19
RIP
ver
sion
2 (
RIP
v2)
�
Mos
t im
port
ant n
ew fe
atur
e w
as to
incl
ude
the
subn
et m
ask
with
the
adve
rtis
ed r
oute
�
Nee
ded
to s
uppo
rt c
lass
less
add
ress
ing
�
Sup
port
for
auth
entic
atio
n
�
Use
s IP
mul
ticas
t des
tinat
ion
addr
ess
�
Rou
te ta
g op
tion
�
For
inte
ract
ion
with
ext
erna
l gat
eway
pro
toco
ls
�
Nex
t-ho
p op
tion
�
Nex
t-ho
p ro
uter
ass
ocia
ted
with
adv
ertis
emen
t
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
20
RIP
v1 p
acke
t for
mat
Packet format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| command (1) | version (1) | must be zero (2) |
+---------------+---------------+-------------------------------+
| |
~ RIP Entry (20) ~
| |
+---------------+---------------+---------------+---------------+
A RIPv1 entry has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| address family identifier (2) | must be zero (2) |
+-------------------------------+-------------------------------+
| IPv4 address (4) |
+---------------------------------------------------------------+
| must be zero (4) |
+---------------------------------------------------------------+
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
21
RIP
v2 p
acke
t for
mat
Packet format is the same, RIPv2 entry format is:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Family Identifier (2) | Route Tag (2) |
+-------------------------------+-------------------------------+
| IP Address (4) |
+---------------------------------------------------------------+
| Subnet Mask (4) |
+---------------------------------------------------------------+
| Next Hop (4) |
+---------------------------------------------------------------+
| Metric (4) |
+---------------------------------------------------------------+
Authentication uses one entry of the format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Command (1) | Version (1) | unused |
+---------------+---------------+-------------------------------+
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
22
Link
sta
te r
outin
g
�
All
rout
ers
have
com
plet
e ne
twor
k to
polo
gy
info
rmat
ion
(dat
abas
e) w
ithin
thei
r are
a
�
Link
sta
te p
acke
ts a
re fl
oode
d to
all
area
rou
ters
�
Eac
h ro
uter
com
pute
s its
ow
n op
timal
pat
h to
a
dest
inat
ion
netw
ork
�
Con
verg
ence
tim
e is
ver
y sh
ort
�
Pro
toco
l com
plex
ity is
hig
h
�
Ens
ures
a lo
op fr
ee e
nviro
nmen
t
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
23
Link
sta
te r
outin
g ill
ustr
ated
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
24
Link
sta
te r
outin
g da
taba
ses
�
Link
sta
te d
atab
ase
�
Con
tain
s la
test
link
sta
te p
acke
t fro
m e
ach
rout
er
�
PA
TH
(pe
rman
ent)
dat
abas
e
�
Con
tain
s (r
oute
r ID
/pat
h co
st/fo
rwar
ding
dire
ctio
n)
trip
les
�
TE
NT
(te
ntat
ive)
dat
abas
e
�
Sam
e st
ruct
ure
as P
AT
H, i
ts e
ntrie
s m
ay b
e ca
ndid
ates
to m
ove
into
PA
TH
�
For
war
ding
dat
abas
e
�
Con
tain
s ID
and
forw
ardi
ng d
irect
ion
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
25
Dijk
stra
's a
lgor
ithm
�
Sta
rt w
ith s
elf a
s ro
ot o
f the
tree
�
(my
ID, p
ath
cost
0, f
orw
ardi
ng d
irect
ion
0) in
P
AT
H
�
For
eac
h no
de in
PA
TH
, exa
min
e its
LS
P
and
plac
e th
ose
neig
hbor
s in
TE
NT
if n
ot
alre
ady
in P
AT
H o
r T
EN
T
�
If T
EN
T is
em
pty,
exi
t, ot
herw
ise
find
ID w
ith
low
est p
ath
cost
and
in T
EN
T a
nd m
ove
it to
P
AT
H
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
26
Dijk
stra
's a
lgor
ithm
illu
stra
ted
1. S
tart
with
A, p
ut A
in P
AT
H, e
xam
ine
A's
LS
P, a
dd B
and
D to
TE
NT
2. B
is lo
wes
t pat
h co
st in
TE
NT
, pla
ce B
in P
AT
H, e
xam
ine
B's
LS
P, p
ut C
,E in
TE
NT
3. D
is lo
wes
t pat
h co
st in
TE
NT
, pla
ce D
in P
AT
H, e
xam
ine
D's
LS
P, f
ound
bet
ter
E p
ath
4. C
is lo
wes
t pat
h co
st in
TE
NT
, pla
ce C
in P
AT
H, e
xam
e C
's L
SP
, fou
nd b
ette
r E
pat
h ag
ain
5. E
is lo
wes
t pat
h co
st in
TE
NT
, pla
ce E
in P
AT
H, e
xam
ine
E's
LS
P (
no b
ette
r pa
ths)
6. T
EN
T is
em
pty,
term
inat
e
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
27
Ope
n sh
orte
st p
ath
first
(O
SP
F)
�
Sta
ndar
dize
d as
RF
C 2
328
(OS
PF
v2)
�
Com
plex
�
Sup
port
s m
ultip
le r
outin
g m
etric
s (t
houg
h ra
rely
use
d)
�
Allo
ws
2 tie
r hi
erar
chy
for
scal
abili
ty
�
Effi
cien
t
�
Goo
d co
nver
genc
e pr
oper
ties
�
Run
s di
rect
ly o
ver
IP
�
Rec
omm
ende
d IG
P b
y th
e IE
TF
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
28
OS
PF
pac
kets
�
Hel
lo
�
Link
mai
nten
ance
�
Exc
hang
e
�
Initi
al e
xcha
nge
of r
outin
g ta
bles
�
Flo
odin
g
�
Incr
emen
tal r
outin
g up
date
s
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
29
OS
PF
dat
abas
e re
cord
s
�
Rou
ter
links
�
Sum
mar
izes
link
s fr
om a
dver
tisin
g ro
uter
�
Net
wor
k lin
ks
�
Tra
nsit
netw
orks
(br
oadc
ast a
nd n
on-b
road
cast
)
�
Sum
mar
y lin
ks
�
Sum
mar
y in
fo a
dver
tised
by
area
bor
der
rout
ers
�
Ext
erna
l lin
ks
�
Impo
rted
rou
ters
, typ
ical
ly fr
om a
EG
P
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
30
Com
mon
OS
PF
hea
der
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version # | Type | Packet length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Router ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Area ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Checksum | AuType |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Authentication |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
31
Inte
rdom
ain
rout
ing
�
Rou
ting
dom
ains
are
inde
pend
ently
fund
ed
�
Rou
ting
dom
ains
do
not t
rust
eac
h ot
her
�
Rou
ting
dom
ains
may
hav
e di
ffere
nt p
olic
ies
�
Sta
tic r
outin
g
�
EG
P -
firs
t int
erdo
mai
n ro
utin
g pr
otoc
ol
�
BG
P -
cur
rent
pat
h ve
ctor
rou
ting
prot
ocol
TD
C37
5 W
inte
r 20
02Jo
hn K
risto
ff -
DeP
aul U
nive
rsity
32
Bor
der
gate
way
pro
toco
l (B
GP
)
�
Cur
rent
ver
sion
4 s
tand
ardi
zed
in R
FC
177
1
�
Run
s ov
er T
CP
�
Seq
uenc
e of
AS
num
bers
com
pris
es p
ath
�
Sel
ect r
oute
bas
ed o
n pr
efer
ence
s of
pat
h(s)
�
Can
edi
t pat
h in
rou
te a
dver
tisem
ents
�
Can
sel
ectiv
ely
adve
rtis
e pa
ths/
rout
es
�
E-B
GP
ver
sus
I-B
GP
TD
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BG
P a
ttrib
utes
�
Des
crib
e ro
utes
in B
GP
upd
ates
�
Con
fusi
ng d
escr
iptio
ns
�
e.g.
Wel
l kno
wn
attr
ibut
es m
ust b
e su
ppor
ted
�
e.g.
Man
dato
ry m
ust b
e pr
esen
t in
the
upda
te
�
Exa
mpl
es
�
AS
pat
h
�
Com
mun
ity
�
Unr
each
able
TD
C37
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Con
fede
ratio
ns
�
Gro
up o
f AS
s th
at a
ppea
r as
a s
ingl
e A
S
�
A fo
rm o
f agg
rega
tion
�
May
sim
plify
rou
ting
polic
ies
�
e.g.
Don
't go
thro
ugh
conf
eder
atio
n X
rat
her
than
sp
ecify
ing
each
AS
in th
e co
nfed
erat
ion
�
Sub
-opt
imal
rou
ting
may
res
ult
�
Mul
tiple
AS
s in
a p
ath
vect
or a
ppea
r as
a lo
op
TD
C37
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35
Mes
sage
type
s
�
Ope
n
�
Firs
t mes
sage
whe
n ne
ighb
ors
com
e up
�
Upd
ate
�
Con
tain
s ro
utin
g in
form
atio
n
�
Not
ifica
tion
�
Fin
al m
essa
ge ju
st b
efor
e lin
k is
dis
conn
ecte
d
�
Kee
paliv
e
�
Rea
ssur
es r
each
abili
ty in
abs
ence
of u
pdat
es
TD
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Rou
te d
ampe
ning
�
Rou
tes
that
osc
illat
e rip
ple
thro
ugh
Inte
rnet
�
Con
sum
es C
PU
and
cau
ses
inst
abili
ty
�
Uns
tabl
e (f
lapp
ing)
rou
tes
are
pena
lized
�
For
som
e pe
riod
of ti
me
rout
e is
sur
pres
sed
�
Sup
ress
ion
time
can
incr
ease
to a
max
imum
�
Sup
ress
ion
of r
oute
s re
sults
in lo
st c
onne
ctiv
ity
�
Big
ger/
impo
rtan
t net
bloc
ks d
ampe
n sl
owly
TD
C37
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Sam
ple
Cis
co B
GP
con
figur
atio
n
Router bgp 12345
bgp log-neighbor-changes
network 128.160.0.0 mask 255.255.0.0
neighbor 36.5.1.1 remote-as 54321
neighbor 36.5.1.1 description E-BGP peer with XYZ corp.
neighbor 36.5.1.1 password as54321password
neighbor 36.5.1.1 version 4
neighbor 36.5.1.1 prefix-list invalid in
neighbor 36.5.1.1 prefix-list announce out
ip prefix-list invalid seq 10 deny 0.0.0.0/8 le 32
ip prefix-list invalid seq 20 deny 10.0.0.0/8 le 32
ip prefix-list invalid seq 30 deny 127.0.0.0/8 le 32
...
ip prefix-list announce seq 10 permit 128.160.0.0/16
ip prefix-list announce seq 20 deny 0.0.0.0/0 le 32
TD
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Fin
al th
ough
ts
�
Rou
ting
prot
ocol
s w
ork
fine
99.9
9% o
f the
tim
e, b
ut w
hen
they
don
't, fa
ilure
s ar
e ge
nera
lly c
atas
trop
hic
�
Tro
uble
shoo
ting
com
plex
rou
ting
prob
lem
s ca
n m
ake
your
bra
in h
urt
�
Gen
eral
ly th
e on
ly n
eces
sary
inte
llige
nce
that
is
req
uire
d in
the
netw
ork
is IP
rou
ting
�
Inte
rnet
pee
ring
is a
fun
issu
e to
exp
lore