2. Microsemi
  3. AN1196 DHCP Pool Per Interface Addresses

Microsemi AN1196 DHCP Pool Per Interface Addresses User guide

  • Hello, I'm your chat assistant. I have analyzed the provided application note about Microsemi's DHCP Pool Per-Interface Addresses. This document details how to configure reserved IP addresses for specific network interfaces within a DHCP pool, allowing a 1:1 mapping between ports and IP. I understand the configuration commands, the concepts of reserved-only and non-reserved pools, and the impact on DHCP bindings. I'm ready to answer any questions you may have about the configuration process or features described in the document.
  • What is the primary use case for per-interface DHCP addresses?
    What is the difference between a reserved-only and not-reserved-only DHCP pool?
    What happens to existing DHCP bindings when changing per-interface address configuration?
AN1196 Software
Conguration Guide - DHCP
Pool Per-Interface Addresses
AN1196
==960.A6<;%<A2
+%'#& !&#"%'#& !&#"%$&"$"
(2C''#

<;P12;A6.9
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
$60?<@2:6 :.82@ ;< D.??.;AF ?2=?2@2;A.A6<; <? 4B.?.;A22 ?24.?16;4 A52
6;3<?:.A6<; 0<;A.6;21 52?26; <? A52 @B6A./696AF <3 6A@ =?<1B0A@ .;1 @2?C602@ 3<? .;F
=.?A60B9.? =B?=<@2 ;<? 1<2@ $60?<@2:6 .@@B:2 .;F 96./696AF D5.A@<2C2? .?6@6;4 <BA
<3 A52 .==960.A6<; <? B@2 <3 .;F =?<1B0A <? 06?0B6A *52 =?<1B0A@ @<91 52?2B;12?
.;1 .;F <A52? =?<1B0A@ @<91 /F $60?<@2:6 5.C2 /22; @B/720A A< 96:6A21 A2@A6;4 .;1
@5<B91 ;<A /2 B@21 6; 0<;7B;0A6<; D6A5 :6@@6<;0?6A60.9 2>B6=:2;A <? .==960.A6<;@
;F =2?3<?:.;02 @=206P0.A6<;@ .?2 /2962C21 A< /2 ?296./92 /BA .?2 ;<A C2?6P21 .;1
BF2? :B@A 0<;1B0A .;1 0<:=92A2 .99 =2?3<?:.;02 .;1 <A52? A2@A6;4 <3 A52 =?<1B0A@
.9<;2 .;1 A<42A52? D6A5 <? 6;@A.9921 6; .;F 2;1=?<1B0A@ BF2? @5.99 ;<A ?29F <;
.;F 1.A. .;1 =2?3<?:.;02 @=206P0.A6<;@ <? =.?.:2A2?@ =?<C6121 /F $60?<@2:6 !A
6@ A52 BF2?I@ ?2@=<;@6/696AF A< 6;12=2;12;A9F 12A2?:6;2 @B6A./696AF <3 .;F =?<1B0A@
.;1 A< A2@A .;1 C2?63F A52 @.:2 *52 6;3<?:.A6<; =?<C6121 /F $60?<@2:6 52?2B;12?
6@ =?<C6121 J.@ 6@ D52?2 6@K .;1 D6A5 .99 3.B9A@ .;1 A52 2;A6?2 ?6@8 .@@<06.A21 D6A5
@B05 6;3<?:.A6<; 6@ 2;A6?29F D6A5 A52 BF2? $60?<@2:6 1<2@ ;<A 4?.;A 2E=9606A9F <?
6:=9606A9F A< .;F =.?AF .;F =.A2;A ?645A@ 9602;@2@ <? .;F <A52? !' ?645A@ D52A52?
D6A5 ?24.?1 A< @B05 6;3<?:.A6<; 6A@293 <? .;FA56;4 12@0?6/21 /F @B05 6;3<?:.A6<;
!;3<?:.A6<; =?<C6121 6; A56@ 1<0B:2;A 6@ =?<=?62A.?F A< $60?<@2:6 .;1 $60?<@2:6
?2@2?C2@ A52 ?645A A< :.82 .;F 05.;42@ A< A52 6;3<?:.A6<; 6; A56@ 1<0B:2;A <? A< .;F
=?<1B0A@.;1@2?C602@.A.;FA6:2D6A5<BA;<A602
About Microsemi
$60?<@2:6 <?=<?.A6<; %.@1.> $) <O2?@ . 0<:=?252;@6C2 =<?A3<96< <3
@2:60<;1B0A<? .;1 @F@A2: @<9BA6<;@ 3<? .2?<@=.02  1232;@2 0<::B;60.A6<;@ 1.A.
02;A2? .;1 6;1B@A?6.9 :.?82A@ '?<1B0A@ 6;09B12 5645=2?3<?:.;02 .;1 ?.16.A6<;
5.?12;21 .;.9<4 :6E21@64;.9 6;A24?.A21 06?0B6A@ '@ )<@ .;1 )!@ =<D2?
:.;.42:2;A =?<1B0A@ A6:6;4 .;1 @F;05?<;6G.A6<; 12C602@ .;1 =?206@2 A6:2
@<9BA6<;@ @2AA6;4 A52 D<?91I@ @A.;1.?1 3<? A6:2 C<602 =?<02@@6;4 12C602@ (
@<9BA6<;@ 16@0?2A2 0<:=<;2;A@ 2;A2?=?6@2 @A<?.42 .;1 0<::B;60.A6<; @<9BA6<;@
@20B?6AF A205;<9<462@ .;1 @0.9./92 .;A6A.:=2? =?<1B0A@ A52?;2A @<9BA6<;@ '<D2?
<C2?A52?;2A !@ .;1 :61@=.;@ .@ D299 .@ 0B@A<: 12@64; 0.=./696A62@ .;1 @2?C602@
$60?<@2:6 6@ 52.1>B.?A2?21 6; 96@< +627< .963<?;6. .;1 5.@ .==?<E6:.A29F 
2:=9<F22@49</.99F#2.?;:<?2.ADDD:60?<@2:60<:
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
1. Introduction
*56@ 1<0B:2;A /?62QF 12@0?6/2@ #!/.@21 [email protected] <3  ' =<<9 =2?6;A2?3.02
.11?2@@2@.9@<8;<D;.@ %&%)%&&&
2. Feature Description
*56@ 32.AB?2 .6:@ A< =?<C612 .; ./696AF A< 0<;P4B?2 .  ' =<<9 @B05 A5.A A52?2 6@ .
 :.==6;4 /2AD22; .; A52?;2A =<?A 6;A2?3.02 .;1 A52 !' .11?2@@ <O2?21 <; 2E.0A9F
A5.A=<?A6;A2?3.02
 =?6:.?F B@20.@2 6@ D52; . @D6A05 12C602 5.@ <;9F <;2 16?20A9F .AA.05 0962;A =2?
=<?A 3<? @<:2 @B/@2A <3 =<?A@ !; A5.A 0.@2 6A 0.; /2 0<;C2;62;A A< 9<08 A52 !' .11?2@@
<3 A52 12C602 .AA.0521 A< 2.05 =<?A .@ A56@ @6:=96P2@ 0962;A 12C602 ?2=9.02:2;A 6; .
=?<1B0A6<; 2;C6?<;:2;A @@B:2 @.F . @2;@<? <3 @<:2 86;1 6@ .AA.0521 A< 6;A2?3.02
Fa 1/4  .;1 A52 @2;@<? :.93B;0A6<;@ *52 @2?C602 A205;606.; D699 @6:=9F 16@0<;;20A
A52 3.696;4 12C602 ?2=9.02 6A .;1 0<;;20A A52 ;2D 12C602 H D5605 D699 A52; C6.  '
?2026C2 2E.0A9F A52 @.:2 !' 0<;P4B?.A6<; .@ A52 3.6921 12C602 !A 6@ A52; <3 0<B?@2
B= A< . ;2AD<?8 :.;.42:2;A @F@A2: A< =2?3<?: .116A6<;.9 0<;P4B?.A6<; <3 A52 ;2D
12C602 63 6A ;221@ 6A /BA .A 92.@A A52 ;2AD<?8 :.;.42:2;A @F@A2: 1<2@;IA 5.C2 A<
@<:25<D@2.?05A52;2AD<?83<?A52?2=9.02:2;A12C602!'
E02=A D52?2 2E=9606A9F ;<A21 .99 :2;A6<;@ <3 .; 6;A2?3.02 .?2 6;
?29.A6<; A< . @=206P0 =<<9 !A 6@ C.961 3<? A52 @.:2 [email protected] 6;A2?3.02 A<
/2 6;09B121 6; :B9A6=92 =<<9@ A5.A @2?C602 16O2?2;A +#% 6;A2?3.02@
<;P4B?.A6<; 0<;@6@A2;0F 6; A5.A 0.@2 6@ A52 ?2@=<;@6/696AF <3 A52
@F@A2:.1:6;6@A?.A<?
2.1. Example
L @@B:2+#%6;A2?3.02D6A5!'
L @@B:2=<?A@ Fa 1/1-4 .?2:2:/2?@<3+#%
L @@B:2D20?2.A2. '=<<93<?A5.A;2AD<?8
L *52;D2D.;AA</2./92A<@.F
N  ' DISCOVER/REQUEST .??6C6;4 <; - . - @5.99 ?2026C2 !' 
N ;1<; Fa 1/2 6A@5.99?2026C2
BA A52; D5.A ./<BA Fa 1/3 .;1 Fa 1/4  !A 12=2;1@ <; D52A52? A52 =<<9 6@ 0<;P4B?21
A< <;9F 5.;1 <BA ?2@2?C21 .11?2@@2@ <? ;<A !3 6A 6@ <;9F A52 AD< .11?2@@2@ 3<? Fa 1/1
.;1 Fa 1/2 .?2.C.69./92 H .;1 Fa 1/3 .;1 Fa 1/4 D<;IA@2?C602 '0962;A@
&; A52 <A52? 5.;1 63 A52 =<<9 6@;IA 9<0821 A< ?2@2?C21 .11?2@@2@ A52; Fa 1/3 .;1 Fa
1/4 D699 5.;1 <BA ;<;?2@2?C21 .11?2@@2@ 3?<: A52 ?2:.6;6;4 3?22 .11?2@@2@ <3 A52
0<;P4B?21=<<9;2AD<?8*52@2A<3?2:.6;6;4.11?2@@6@
L *52!';2AD<?8:6;B@
N *52+#%6;A2?3.02.11?2@@24
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
N *52@2A<3=2?6;A2?3.02.11?2@@2@.;1
N ;F2E09B121.11?2@@?.;42@
N ;1.;F.9?2.1F.0A6C2 '0962;A.11?2@@2@
*52?292C.;A=.?A@<3A520<;P4B?.A6<;D<B919<<8@6:69.?A<A56@
# show running-config
! Globally enable the DHCP server function
ip dhcp server
! Create the VLAN and VLAN interface that will be serving DHCP
vlan 42
interface vlan 42
ip address 10.42.0.1 255.255.0.0
ip dhcp server
! (Port VLAN membership setup omitted)
! Create the pool
ip dhcp pool my_pool
network 10.42.0.0 255.255.0.0
broadcast 10.42.255.255
lease 1 0 0
! Specify per-interface addresses for Fa 1/1 and Fa 1/2:
address 10.42.1.100 interface FastEthernet 1/1
address 10.42.55.3 interface FastEthernet 1/2
! Only hand out per-interface addresses:
! reserved-only
! Or hand out both per-interface addresses and normal dynamic addresses
! no reserved-only
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
3. Reserved-Only vs. Not Reserved-Only
*52 ./<C2 0<;P4B?.A6<; 0.; /2 699B@A?.A21 .@ 3<99<D@ *52  ' )2?C2? )D6A05 5.@
;B:2?<B@ 6;A2?3.02@ D6A5 0962;A@ .AA.0521 &;2 <3 A5<@2 0962;A@ 6@ . @6:=92 9.F2? 
2A52?;2A @D6A05 D6A5 A5?22 .AA.0521 0962;A@ *52 AD< P?@A 6;A2?3.02@ <; A52  '
)2?C2? )D6A05 5.;1 <BA A52 =2?6;A2?3.02 .11?2@@2@ .;1 A52 ?2:.6;6;4 6;A2?3.02@
5.;1<BA.C.69./92.11?2@@2@3?<:A52=<<9
*52#.F2?)D6A056@.@@B:21A<5.C2.@A.A60!'
DHCP
Server
Switch
10.42.1.100
10.42.55.3
10.42.0.2 Layer 2
Switch
10.42.0.3
10.42.0.4
10.42.0.5
10.42.0.6
Fa 1/1
Fa 1/2
Fa 1/3
Fa 1/5
Fa 1/4
(%$$!'%#'%%&&&$'&%)#!+
!3 5<D2C2? A52 =<<9 6@ =9.021 6; ?2@2?C21<;9F :<12 <;9F A52 AD< 0962;A@ .AA.0521 A<
..;1.D699/2<O2?21.11?2@@2@
Switch# configure terminal
Switch(config)# ip dhcp pool my_pool
Switch(config-dhcp-pool)# reserved-only
Switch(config-dhcp-pool)# end
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
DHCP
Server
Switch
10.42.1.100
10.42.55.3
Layer 2
Switch
Fa 1/1
Fa 1/2
Fa 1/3
Fa 1/5
Fa 1/4
(%$$!'%#'%%&&&&%)#!+
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
*56@ D<B91 .9@< .==9F 63 A52 9.F2?  @D6A05 D.@ .AA.0521 A< 24 .  &;9F <;2 <3 6A@
0962;A@D<B91/2<O2?21A52=2?6;A2?3.02.11?2@@
DHCP
Server
Switch
10.42.55.3
Layer 2
Switch 10.42.1.100
Fa 1/2
Fa 1/3
Fa 1/1
Fa 1/4
Fa 1/5
(%$$!'%#'%%&&&*'$#%#'%$%'
!3 A52 =<<9 6@;IA ?2@2?C21<;9F A52 @.:2 @6AB.A6<; .==962@ A< A52 # )D6A05 0962;A@ &;9F
<;2 <3 A52: D699 /2 <O2?21 .; .11?2@@ D52?2.@ A52 0962;A@ 16?20A9F 0<;;20A21 A< A52
 ' )2?C2? )D6A05 <; 6;A2?3.02@ D6A5<BA . =2?6;A2?3.02 .11?2@@ D699 .99 /2 <O2?21
.11?2@@2@3?<:A52=<<9
DHCP
Server
Switch
10.42.55.3
10.42.0.2 Layer 2
Switch
10.42.0.3
10.42.1.100
10.42.0.4
Fa 1/2
Fa 1/3
Fa 1/1
Fa 1/4
Fa 1/5
(%$$!'%#'%%&&&$'&%)#!+
!; A56@ 0.@2 A52 A5?22 0962;A@ .AA.0521 A< A52 #.F2?  @D6A05 D699
0<:=2A2 3<? A52 @<92 .C.69./92 .11?2@@ <O2?21 /F .  <; A52  '
)2?C2? )D6A05 !A 6@ 42;2?.99F ;<;12A2?:6;6@A60 D5605 12C602 D6;@
@<A56@0<;P4B?.A6<;@5<B91/2.C<6121
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
4. Con$guration
'2?6;A2?3.02 .11?2@@2@ .?2 .C.69./92 3<?  ' =<<9@ <3 AF=2 ;2AD<?8 <;9F *52F 1<
;<A:.82@2;@23<?5<@A=<<9@.@A5<@2<;9F5.C2<;2.11?2@@A<<O2?.;FD.F
*52 3<99<D6;4 3<B? 0<;P4B?.A6<; 0<::.;1@ .?2 .C.69./92 6; A52  ' =<<9
0<;P4B?.A6<;@B/:<12
!%#'%%&&$#,(%'$#$""#&
Command Description
address <ipv4_address> interface
<interface_name>
?2.A2:<163F.=2?6;A2?3.02.11?2@@
2;A?F
no address <ipv4_address> 292A2.=2?6;A2?3.02.11?2@@2;A?F
reserved-only &;9F<O2?=2?6;A2?3.02.11?2@@2@
no reserved-only &O2?/<A5=2?6;A2?3.02.11?2@@2@.;1
;<?:.91F;.:60.11?2@@2@3?<:A52
=<<9
*523<99<D6;4?B92@.==9F
L ;6;A2?3.020.;5.C2<;9F<;2=2?6;A2?3.02.11?2@@
L 99=2?6;A2?3.02.11?2@@2@:B@A/2B;6>B2
L ; 6;A2?3.02 D6A5 . =2?6;A2?3.02 .11?2@@ D699 <;9F <O2? A5.A <;2 .11?2@@ A< 0962;A@
L =2?6;A2?3.02.11?2@@:B@A/29<;4A<A52=<<9;2AD<?8
*52 ./<C2 ?B92@ .?2 =2? =<<9  =.?A60B9.? [email protected] =<?A 0.; /2
:2:/2? <3 16O2?2;A +#%@ .;1 16O2?2;A =<<9@ .;1 <O2? 16O2?2;A
=2?6;A2?3.02.11?2@@2@6;2.05=<<9
5.;46;4 =2?6;A2?3.02 .11?2@@ 0<;P4B?.A6<; 3<? .; 2E6@A6;4 =<<9
:.F6;C.961.A22E6@A6;4/6;16;4@
*52?B92@4<C2?;6;4/6;16;42E=6?F.?2
Lreserved-only Mno reserved-only  "22= /6;16;4@ A52 =<<9 <3 .C.69./92
.11?2@@2@@6:=9F4?<D@
Lno reserved-only Mreserved-only 92.?.99/6;16;4@
L 11 <? 5.;42 =2?6;A2?3.02 .11?2@@ 92.? .99 /6;16;4@ 6A 0<B91 /2 .; .9?2.1F6;
B@2!'<?.;6;A2?3.02D6A5<A52?.0A6C2/6;16;4@
L 292A2=2?6;A2?3.02.11?2@@92.?/6;16;43<?A5.A.11?2@@<;9F
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
L #6;81<D; <; .; 6;A2?3.02 D6A5 . =2?6;A2?3.02 .11?2@@ 92.? A52 /6;16;4 *56@
2;@B?2@ A5.A A52 16?20A9F 0<;;20A21 0962;A 12C602 ?2=9.02:2;A @02;.?6< D<?8@
,52; A52 3.6921 12C602 6@ ?2:<C21 96;81<D; 2;@B2@ ,52; A52 ?2=9.02:2;A
12C602 =<D2?@ B= .;1 96;8B= 2;@B2@ A56@ 12C602 D699 </A.6; A52 =2?6;A2?3.02
.11?2@@
116;4 . ?2@2?C21 2;A?F <; .; 6;A2?3.02 A5.A 5.@ :B9A6=92 2E6@A6;4
0962;A@ 6:=962@ A5.A A52 2E6@A6;4 0962;A@ D<;IA /2 ./92 A< ?2;2D A526?
/6;16;4@ A52F :B@A 0<:=2A2 3<? A52 @6;492 .C.69./92 .11?2@@ <; A52
6;A2?3.02 *56@ D699 B9A6:.A29F 92.C2 .99 /BA <;2 0962;A D6A5<BA  '
@2?C21!'
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
5. Monitoring
'2?6;A2?3.02 .11?2@@2@ 6;A?<1B02 ;< ;2D :<;6A<?6;4 0<::.;1@ /BA :2?29F 2EA2;1@
A52<BA=BA3?<:02?A.6; '=<<9:<;6A<?6;40<::.;1@
!%#'%%&&$#'$%#$""#&
Command Description
show ip dhcp pool [<pool_name>] 6@=9.F=2?=<<96;3<?:.A6<;99=<<9@
.?296@A2163A52 pool_name 6@<:6AA21
show ip dhcp server binding […] 6@=9.F/6;16;46;3<?:.A6<;)2C2?.9
P9A2?@.?2.C.69./923<?P9A2?6;4<;
@A.A2.;1<?AF=2
E.:=92@
@0.;/2@22;A52=2?6;A2?3.02.11?2@@2@.?296@A21.AA522;1<3A52<BA=BA
Switch# show ip dhcp pool
Pool Name: my_pool
----------------------------------------------
Type is network
IP is 10.42.0.0
Subnet mask is 255.255.0.0
Subnet broadcast address is 10.42.255.255
Lease time is 1 days 0 hours 0 minutes
Default router is -
Domain name is -
DNS server is -
NTP server is -
Netbios name server is -
Netbios node type is -
Netbios scope identifier is -
NIS domain name is -
NIS server is -
Vendor class information is -
Client identifer is -
Hardware address is -
Client name is -
Is restricted to reserved addresses:
10.42.1.100 on interface FastEthernet 1/1
10.42.55.3 on interface FastEthernet 1/2
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
*52./<C2<BA=BA@5<D@A5.AA52!'6@0B??2;A9F0<::6AA21A<.0962;A
Switch# show ip dhcp server binding
IP: 10.42.1.100
----------------------------------------------
State is committed
Binding type is automatic
Pool name is my_pool
Server ID is 10.42.0.1
VLAN ID is 42
Subnet mask is 255.255.0.0
Client identifier is type of MAC address that is ..:..:..:..:..:..
Hardware address is ..:..:..:..:..:..
Lease time is 1 days 0 hours 0 minutes 0 seconds
Expiration is 12 hours 39 minutes 8 seconds
%%)<3AD.?2<;P4B?.A6<;B612 ''<<9'2?
!;A2?3.0211?2@@2@
==960.A6<;
%<A2
 <;P12;A6.9 '.42<3
/