CONFIGURING REMOTE SITES TO REACH THE CORE SWITCH 4

[drbk563]

Here is the situation. The layout of the network can be found at

http://www.virgoletta.com.

What I am trying to do is connect the four sites connect to the Hub router using EIGRP so that each site can talk to each other. What should happen is that all the users behind each router at each site should be able to reach core switch to reach the internet. I need some help with the configuration to get this working. In addition, the users at each site must get an ip address assigned to them via a DHCP server(143.104.179.1) which is located at the same location as the core switch.

Below is the config so far for the Hub Router and remote site 4. Please advise on what should be added or changed to get this working correctly.

Thank you in advance

Hub Router

interface GigabitEthernet0/0
ip address 143.104.179.239 255.255.255.0
duplex auto
speed auto
media-type rj45
negotiation auto
!
interface GigabitEthernet0/1
no ip address
shutdown
duplex auto
speed auto
media-type rj45
negotiation auto
!
interface Serial0/0/0:0
ip address 2.2.2.1 255.255.255.252
!
interface Serial0/0/1:1
description Circuit 32HCGS342365
ip address 2.2.3.1 255.255.255.252
!
interface Serial0/1/0:1
description Circuit 32HCGS342436
ip address 2.2.4.1 255.255.255.252
!
interface Serial0/1/1:1
description Circuit 32HCGS342273
ip address 2.2.5.1 255.255.255.252
!
router eigrp 101
network 2.2.2.0 0.0.0.3
network 2.2.3.0 0.0.0.3
network 2.2.4.0 0.0.0.3
network 2.2.5.0 0.0.0.3
no auto-summary
!
ip route 0.0.0.0 0.0.0.0 143.104.179.254

*************************************************************

Remote Site 4

interface FastEthernet0/0
ip address 3.3.3.2 255.255.255.192
ip helper-address 143.104.179.1
speed 100
full-duplex

interface Serial0/1
ip address 2.2.2.2 255.255.255.252
service-module t1 timeslots 1-24
!
router eigrp 101
network 2.2.2.0 0.0.0.3
no auto-summary

 

[plshlpme]

sorry.. lan interfaces not wan

 

[plshlpme]

http://www.cisco.com/univercd/cc/td...1/121cgcr/ip_r/iprprt1/1rdipadr.htm#wp1018606

One common application that requires helper addresses is Dynamic Host Configuration Protocol (DHCP), which is defined in RFC 1531. DHCP protocol information is carried inside of BOOTP packets. To enable BOOTP broadcast forwarding for a set of clients, configure a helper address on the router interface closest to the client. The helper address should specify the address of the DHCP server. If you have multiple servers, you can configure one helper address for each server. Because BOOTP packets are forwarded by default, DHCP information can now be forwarded by the router. The DHCP server now receives broadcasts from the DHCP clients.

 

[Minue]

Hi plshlpme
When I was studying CCNA,it was thought that ip address helper command goes on the LAN link.The gateway is responsible for forwarding the broadcast because the WAN can't see the broadcast.
I could be wrong!Please advice.
Regards

 

[plshlpme]

no your right.. i corrected myself right after i hit submit

the little quote i posted says:

"configure a helper address on the router interface closest to the client"

so to be clear..

ip helper-address goes on the spoke sites LAN interface

 

[burtsbees]

But if the DHCP server is on the other side of the "hub" router, how will the hub router forward the DHCP broadcasts to the spoke LAN routers? Refer to the diagram drbk563 posted in the first post of this thread.

Burt

 

[drbk563]

So do I have to add the ip-helper address command on the serial ports?

 

[burtsbees]

I think so---fairly certain that you do. But please enlighten us as to your choice to use a DHCP server rather than the router?

Burt

 

[Minue]

Hi Burt
I have pull out my CCNA docs,and really the command only goes on the LAN interface.Will run the above configuration through my LAB and post the results.
Regards

 

[plshlpme]

i was under the impression that the spoke router would take the broadcast and forward it as a unicast so that the upstream routers wouldnt see it as a broadcast anymore.

 

[dearingkr]

See thread557-857082

MCSE CCNA CCDA

 

[burtsbees]

Not ip helper-address, but the ip forward-protocol. Sorry...

http://www.cisco.com/en/US/products...erence_chapter09186a0080087387.html#wp1085207

 

[Minue]

Hello Burt
If you read the article well,you will note that this command complements the ip helper-address command.But it doesn't replace it.
Hi guys lets get or act together.We are making more confusion than needed.I am going to run the example network through a lab,so I can state for sure if it's possible if the plan setup could work.
Regards

 

[plshlpme]

ive checked and we have it running in production networks with the ip-helper on the lan interfaces

 

[Minue]

Hello Guys
Just finish running the example network through my LAB.And it's awesome!Fully working,with the ip helper address command.I thought I would have problems getting the broadcast packet to cross the serial (WAN)line.But all hops just routes the packet without any problem.

But drbk563 be advice this command will keep your serial lines busy with unicast/broadcast packet.You should turn of the other 7 protocols that this command permits.
Good luck wit setting up your network.
Regards

 

[burtsbees]

Like I say...how does the hub router forward the DHCP request broadcasts from the LAN clients THRU the hub router and to the DHCP server segment?

Burt

 

[dearingkr]

The router forwards DHCP requests (broadcasts) to the DHCP server using the following command:

config t
int f0/0
ip helper-address [highlight] x.x.x.x [/highlight]

where x.x.x.x is the ip address of the DHCP server somewhere else on the network.

MCSE CCNA CCDA

 

[Minue]

Hi Burtsbees
Seeing is believing!!!If you want I can send you the Lab topology.So you can try it out in your LAB.To convince yourself do the debug ip packets on the routers so as to see how these packets are handle.As I said I was in doubt before I tried it.
Regards

 

[plshlpme]

Hey guys im going to say this one more time so please read it lol..

when the router receives a broadcast request for dhcp and has the ip helper-address command applied it will take that broadcast and forward it to the dhcp server as a UNICAST.

up and down stream routers will not need the helper-address assigned because it will no longer be a broadcast packet.

the reply is also unicast and is sent directly to the host that requested it.

so this is why you dont need to put the helper commands onto the hub router.

 

[dearingkr]

See below for a diagram and configs for a working site.
One of my clients has a HQ and 5 remote branches.
They have 5 point-point links.
All DHCP, DNS, and internet go through the HQ for centralized access control.

Here is an example of one of the p-to-p sites:

Internet
|
|
Public IP
Firewall
10.10.1.1/24
|
|
Switch------F0/0 10.10.1.3/24 F0/0 10.10.2.3/24-----Switch
10.10.1.2 Router HQ Router Branch 10.10.2.2
| GW 10.10.1.1 GW 10.10.2.1 |
| S0/0 10.10.201.1/30====S0/0 10.10.201.2/30 |
| |
|----------------------------| |
| | |
Workstations (DHCP) DHCP/DNS Server Workstations (DHCP)
10.10.1.x/24 10.10.1.10/24 10.10.2.x/24
GW 10.10.1.3 GW 10.10.1.3 GW 10.10.2.3


DHCP Server configuration
Scope HQ
RAnge 10.10.1.100 - 10.10.1.200
Gateway 10.10.1.3
DNS 10.10.1.10

Scope Branch1
Range 10.10.2.100 - 10.10.2.200
Gateway 10.10.2.3
DNS 10.10.1.10

Scope Branch2
Range 10.10.2.300 - 10.10.3.200
Gateway 10.10.3.3
DNS 10.10.1.10

etc.


Configs

HEADQUARTERS ROUTER

service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname routerhq
!
no logging console
enable secret 5 xxxxx
enable password xxxxx
!
no ip finger
!
no ip subnet-zero
!
interface FastEthernet0/0
description whatever
ip address 10.10.1.3 255.255.255.0
no ip mroute-cache
speed auto
half-duplex
!
interface Serial0/0
ip address 10.10.201.1 255.255.255.252
!
router eigrp 10
network 10.10.0.0 0.0.255.255
auto-summary
!
ip default-gateway 10.10.1.1
ip http server
ip classless
ip route 0.0.0.0 0.0.0.0 10.10.1.1
!
line con 0
password xxxxx
login
line aux 0
line vty 0 4
password xxxxx
login
!
end

BRANCH1 ROUTER
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname routerbranch1
!
no logging console
enable secret 5 xxxxx
enable password xxxxx
!
no ip finger
!
no ip subnet-zero
!
interface FastEthernet0/0
description whatever
ip address 10.10.2.3 255.255.255.0
ip helper-address 10.10.1.10
no ip mroute-cache
speed auto
half-duplex
!
interface Serial0/0
ip address 10.10.201.2 255.255.255.252
!
router eigrp 10
network 10.10.0.0 0.0.255.255
auto-summary
!
ip default-gateway 10.10.201.1
ip http server
ip classless
ip route 0.0.0.0 0.0.0.0 10.10.201.1
!
line con 0
password xxxxx
login
line aux 0
line vty 0 4
password xxxxx
login
!
end



If your circuit is not a full T1, then the telco will give you channel assignments. The serial interface config will look something like this for a 256k circuit:

interface Serial0/0
description whatever
ip address x.x.x.x 255.255.255.252
no fair-queue
service-module t1 timeslots 1-4
!

If your circuit is frame-relay, then you will have to include encapsulation and DLCI statements, such as:

interface Serial0/0
no ip address
encapsulation frame-relay
frame-relay lmi-type ansi

interface Serial 0/0.1
description whatever
ip address x.x.x.x 255.255.255.252
frame-relay interface DLCI xxx

Of course you'll have to fill in the blanks, like specific ip addresses, passwords, hostname, etc.

Please note that these configs have no 'lockdown' procedures, access lists, etc.



MCSE CCNA CCDA

 

[burtsbees]

Okay---after this I will let this go...
The man has a DHCP server on one LAN. This LAN goes to a Core Switch, which is attached to the Hub Router. Also attached to the Hub Router are 4 point-to-point sites, which have clients that need DHCP assigned. They request this via BROADCAST through the Hub Router to the Core Switch to the DHCP server. Since the request is a broadcast, I was asking how the Hub Router passes these broadcasts to the DHCP server without having the ip-helper command in the Hub Router as well...
"when the router receives a broadcast request for dhcp and has the ip helper-address command applied it will take that broadcast and forward it to the dhcp server as a UNICAST."
in other words, doesn't the Hub Router need the ip-halper address command as well?

Burt