DHCP Pool Static Client Configuration(Cisco IOL)

1. DHCP Pool Static Client Configuration 구성도

1) DHCP Pool Static Client Configuration 구성도

• DHCP 기본 개념, DHCP 동작 과정, DHCP Basic Configuration을 먼저 학습하는 것을 권고

 

2) 테스트 장비

• Emulator : EVE-NG
• OS : Cisco IOL I86BI_LINUXL2-ADVENTERPRISEK9-M, Version 15.1c

 

 

2. DHCP Pool Static Client Configuration

1) DHCP Server SVI Configuration

< VLAN 생성 >
DHCP-SERVER(config)#vlan 10
DHCP-SERVER(config-vlan)#name VLAN10

< Interface에 VLAN Bidning >
DHCP-SERVER(config)#interface e0/0
DHCP-SERVER(config-if)#switchport mode access
DHCP-SERVER(config-if)#switchport access vlan 10
DHCP-SERVER(config-if)#no cdp enable

DHCP-SERVER(config)#interface e0/1
DHCP-SERVER(config-if)#switchport mode access
DHCP-SERVER(config-if)#switchport access vlan 10
DHCP-SERVER(config-if)#no cdp enable

< VLAN Interface에 IP Address 구성 >
DHCP-SERVER(config)#interface vlan 10
DHCP-SERVER(config-if)#ip address 10.0.0.1 255.255.255.0
DHCP-SERVER(config-if)#no shutdown

 

2) DHCP Pool Configuration

DHCP-SERVER(config)#ip dhcp pool AUTO-POOL					## DHCP POOL 설정
DHCP-SERVER(dhcp-config)#network 10.0.0.0 255.255.255.0		## Network Address 설정
DHCP-SERVER(dhcp-config)#default-router 10.0.0.1			## 클라이언트에게 전달할 Gateway 설정
DHCP-SERVER(dhcp-config)#lease 0 0 2						## Lease Time 설정(1min)
DHCP-SERVER(config)#ip dhcp excluded-address 10.0.0.1 10.0.0.10		## 클라이언트에게 할당하지 않을 IP Address Range 구성

DHCP-SERVER(config)#ip dhcp pool STATIC-POOL				## DHCP POOl 설정
DHCP-SERVER(dhcp-config)#host 10.0.0.100 255.255.255.0		## Static으로 지정할 Host IP 설정
DHCP-SERVER(dhcp-config)#default-router 10.0.0.1
DHCP-SERVER(dhcp-config)#client-identifier 01aa.bbcc.0370.00	## Static으로 구성할 Client-ID 지정
DHCP-SERVER(dhcp-config)#lease 0 0 5

• "client-identifier" 명령어 입력 시, 앞에 "01"을 추가하여 설정
• "host x.x.x.x"와 "network x.x.x.x" 명령을 동일한 Pool에 설정이 불가능하므로 서로 다른 Pool에 구성
• "STATIC-POOL"에 구성한 Client-ID를 가진 클라이언트가 Discover 메시지 전송 시, 해당 IP Address를 할당

 

3) DHCP Client Configuration

CLIENT-1(config)#interface e0/0
CLIENT-1(config-if)#no switchport 
CLIENT-1(config-if)#ip address dhcp client-id Ethernet0/0	##e0/0 인터페이스의 MAC 주소를 Client-ID로 사용
CLIENT-1(config-if)#no shutdown

• DHCP 서버는 IP 할당 시, IP 충돌 확인을 위해 ARP Request를 전송하고 Reply가 수신되지 않으면 Offer 메시지를 전송하지만 Static으로 구성하면 ARP Request를 전송하지 않고 바로 Offer 메시지를 전송

 

• 아래 한 가지를 제외하고 DHCP 메시지는 일반적인 DHCP 메시지와 동일
  • Renewal, Rebinding, Release 동작 때 발생하는 메시지도 일반적인 DHCP 메시지와 동일
• 클라이언트는 DHCP 메시지를 전송할 때 "Client identifier(Option 61)" 값을 위에서 설정한 Interface MAC Address로 구성하여 전송하는 차이점만 존재

 

4) DHCP Client 확인

CLIENT-1#show ip route | begin Gateway
Gateway of last resort is 10.0.0.1 to network 0.0.0.0

S*    0.0.0.0/0 [254/0] via 10.0.0.1
      10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C        10.0.0.0/24 is directly connected, Ethernet0/0
L        10.0.0.100/32 is directly connected, Ethernet0/0

CLIENT-1#show dhcp server
   DHCP server: ANY (255.255.255.255)
    Leases:   45
    Offers:   3      Requests: 45     Acks : 45     Naks: 0
    Declines: 0      Releases: 6     Query: 0     Bad: 0
    Subnet: 255.255.255.0   DNS Domain: CISCO.COM

CLIENT-1#show dhcp lease 
Temp IP addr: 10.0.0.100  for peer on Interface: Ethernet0/0
Temp  sub net mask: 255.255.255.0
   DHCP Lease server: 10.0.0.1, state: 5 Bound
   DHCP transaction id: 20B4
   Lease: 300 secs,  Renewal: 150 secs,  Rebind: 259 secs
Temp default-gateway addr: 10.0.0.1
   Next timer fires after: 00:00:58
   Retry count: 0   Client-ID: aabb.cc03.7000
   Client-ID hex dump: AABBCC037000
   Hostname: CLIENT-1

• Client-ID가 e0/0 인터페이스의 MAC Address로 구성된 것을 확인

 

5) DHCP Server 확인

DHCP-SERVER#show ip dhcp pool 

Pool AUTO-POOL :
 Utilization mark (high/low)    : 100 / 0
 Subnet size (first/next)       : 0 / 0 
 Total addresses                : 254
 Leased addresses               : 0
 Excluded addresses             : 11
 Pending event                  : none
 1 subnet is currently in the pool :
 Current index        IP address range                    Leased/Excluded/Total
 10.0.0.1             10.0.0.1         - 10.0.0.254        0     / 11    / 254  

Pool STATIC-POOL :
 Utilization mark (high/low)    : 100 / 0
 Subnet size (first/next)       : 0 / 0 
 Total addresses                : 1
 Leased addresses               : 1
 Excluded addresses             : 1
 Pending event                  : none
 0 subnet is currently in the pool :
 Current index        IP address range                    Leased/Excluded/Total
 10.0.0.100           10.0.0.100       - 10.0.0.100        1     / 1     / 1

DHCP-SERVER#show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address          Client-ID/              Lease expiration        Type
                    Hardware address/
                    User name
10.0.0.100          01aa.bbcc.0370.00       Infinite                Manual

• Client-ID가 e0/0 인터페이스의 MAC Address로 구성된 것을 확인
• 서버에서 Client-ID를 Binding 할 때, MAC Address 앞에 "01"을 추가하므로 "STATIC-POOL"에서 해당 값을 추가한 것