12-07-2017 03:52 PM - edited 03-05-2019 09:36 AM
Hi,
I'm trying to simulate a PPPoE Server-SOHO Clients network in my lab and I can't make it to work. I'm not sure if I am missing something, so I badly need your help.
Here's the setup:
Cisco 2600 router is to be configured as PPPoE Server. One ethernet port of the router is connected to the Internet source, while the second ethernet port is connected to a Cisco switch that is also connected to 2 Windows computers (that will be used as PPPoE clients).
My problems:
1. PPPoE clients are not getting the correct subnet mask; instead of /24, clients are getting /32.
2. Clients do not have (or not receiving) default gateway. The only info they get from the DHCP server are: IP address, subnet mask (which is incorrect), and DNS server.
Below is the router config:
!
hostname PPPoE_Server
!
!
ip dhcp excluded-address 192.168.10.1 192.168.10.5
!
!
ip dhcp pool PPPoE_Clients
network 192.168.10.0 255.255.255.0
default-router 192.168.10.1
dns-server 8.8.8.8
!
!
username MOMO password 123456789
!
!
bba-group pppoe PPPoE_LAB
virtual-template 1
!
!
interface FastEthernet0/0
description INTERNET_SOURCE
ip address 172.16.255.254 255.255.255.0
ip nat outside
duplex auto
speed auto
!
!
interface FastEthernet0/1
no ip address
duplex auto
speed auto
!
!
interface FastEthernet0/1.30
description SIMULATION_PPPoE
encapsulation dot1Q 30
ip nat inside
ip virtual-reassembly
pppoe enable group PPPoE_LAB
!
!
interface Virtual-Template1
ip address 192.168.10.1 255.255.255.0
peer default ip address dhcp-pool PPPoE_Clients
ppp authentication chap callin
!
Will really appreciate it if you can help me.
Solved! Go to Solution.
12-07-2017 04:46 PM
Hi Momo,
1. PPPoE clients are not getting the correct subnet mask; instead of /24, clients are getting /32.
This is expected. Keep in mind that this is still PPP protocol, just carried on top of Ethernet framing. In PPP, a netmask has no meaning - that is why it is called "point-to-point". From the viewpoint of each client, there is just the client and the PPPoE access concentrator, so the client uses a netmask of /32 for itself. This is completely okay and just the way it is supposed to be.
2. Clients do not have (or not receiving) default gateway. The only info they get from the DHCP server are: IP address, subnet mask (which is incorrect), and DNS server.
I believe that they actualy receive their default gateway, but if you are using Windows as clients, these often do not display the IP default gateway address for PPPoE connections properly. Either way, they should install the default route through the PPPoE connection.
Checking through your configuration, there is a couple of changes I would like to propose:
hostname PPPoE_Server ! ip dhcp excluded-address 192.168.10.1 192.168.10.5 ! ip dhcp pool PPPoE_Clients network 192.168.10.0 255.255.255.0 default-router 192.168.10.1 dns-server 8.8.8.8 ! username MOMO password 123456789 ! bba-group pppoe PPPoE_LAB virtual-template 1 ! interface FastEthernet0/0 description INTERNET_SOURCE ip address 172.16.255.254 255.255.255.0 ip nat outside duplex auto speed auto ! interface FastEthernet0/1 no ip address duplex auto speed auto ! interface FastEthernet0/1.30 description SIMULATION_PPPoE encapsulation dot1Q 30ip nat inside ip virtual-reassemblypppoe enable group PPPoE_LAB !
interface Loopback0
ip address 192.168.10.1 255.255.255.255
! interface Virtual-Template1ip address 192.168.10.1 255.255.255.0
ip unnumbered Loopack0
ip nat inside
ip mtu 1492
ip tcp adjust-mss 1452
ppp mtu adaptive peer default ip address dhcp-pool PPPoE_Clients ppp authentication chapcallin
To shortly sum up the changes:
Try this out - and feel welcome to ask further!
Best regards,
Peter
12-07-2017 04:46 PM
Hi Momo,
1. PPPoE clients are not getting the correct subnet mask; instead of /24, clients are getting /32.
This is expected. Keep in mind that this is still PPP protocol, just carried on top of Ethernet framing. In PPP, a netmask has no meaning - that is why it is called "point-to-point". From the viewpoint of each client, there is just the client and the PPPoE access concentrator, so the client uses a netmask of /32 for itself. This is completely okay and just the way it is supposed to be.
2. Clients do not have (or not receiving) default gateway. The only info they get from the DHCP server are: IP address, subnet mask (which is incorrect), and DNS server.
I believe that they actualy receive their default gateway, but if you are using Windows as clients, these often do not display the IP default gateway address for PPPoE connections properly. Either way, they should install the default route through the PPPoE connection.
Checking through your configuration, there is a couple of changes I would like to propose:
hostname PPPoE_Server ! ip dhcp excluded-address 192.168.10.1 192.168.10.5 ! ip dhcp pool PPPoE_Clients network 192.168.10.0 255.255.255.0 default-router 192.168.10.1 dns-server 8.8.8.8 ! username MOMO password 123456789 ! bba-group pppoe PPPoE_LAB virtual-template 1 ! interface FastEthernet0/0 description INTERNET_SOURCE ip address 172.16.255.254 255.255.255.0 ip nat outside duplex auto speed auto ! interface FastEthernet0/1 no ip address duplex auto speed auto ! interface FastEthernet0/1.30 description SIMULATION_PPPoE encapsulation dot1Q 30ip nat inside ip virtual-reassemblypppoe enable group PPPoE_LAB !
interface Loopback0
ip address 192.168.10.1 255.255.255.255
! interface Virtual-Template1ip address 192.168.10.1 255.255.255.0
ip unnumbered Loopack0
ip nat inside
ip mtu 1492
ip tcp adjust-mss 1452
ppp mtu adaptive peer default ip address dhcp-pool PPPoE_Clients ppp authentication chapcallin
To shortly sum up the changes:
Try this out - and feel welcome to ask further!
Best regards,
Peter
12-07-2017 06:01 PM
Hi Peter,
Thank you so much for your prompt reply. I will surely try your proposed changes and give you feedback. What I'm trying to accomplish here is to simulate the connection with DSL ISP, where, using PPPoE protocol, we can connect our regular home routers to their modems.
12-07-2017 06:05 PM
12-09-2017 04:19 PM - edited 12-10-2017 01:40 PM
Hi Peter,
I implemented the changes you proposed and here are my observations:
1. Windows PPPoE clients connected directly to the PPPoE server get IP address, /32 subnet mask, and DNS address thru DHCP, but no default gateway. However, everything seems to work perfectly and online.
2. When I connected Linksys and Netgear home routers (as PPPoE client), they were able to connect to the PPPoE server. They get IP address, /32 subnet mask, correct default gateway, but no DNS address. Homes routers are online. Hosts behind the home routers can ping public IP addresses (therefore they are online), but they cannot translate the the domain names. However, everything works perfectly if I set static DNS on the home routers.
I'm still currently researching/investigating what may have caused why home routers cannot get DNS address (thru DHCP) from PPPoE server.
UPDATE: I added the following configuration and it seems to address the problem with home routers. But i'm still observing the connection.
!
interface Virtual-Template1
ppp ipcp dns 8.8.8.8
!
If you have an idea, please let me know. I would really appreciate it.
12-10-2017 04:03 PM
12-10-2017 08:09 PM
Hi Francesco,
You mean route print of Windows clients connected 1)directly to the PPPoE server, and 2)through the homes routers?
12-10-2017 08:12 PM
12-10-2017 09:31 PM
Actually, there were no problems with any Windows clients connected directly to the PPPoE server. These clients do have 1) IP address, 2) /32 subnet mask, and 3)DNS address. All of them were online with no problem.
Problems are with those clients connected through the home routers (Linksys and Netgear) to connect to the PPPoE server. It turned out that home routers that were connected to the PPPoE server were only getting 1)IP address, 2) /32 subnet mask, and 3)default gateway. They do not get DNS address from the PPPoE server. Hence, clients behind the home routers cannot resolve domain names.
This problem was resolved using the following options:
1. Setting static DNS on the home routers.
2. Configuring 'ppp ipcp dns x.x.x.x' command under Interface Virtual-template
12-11-2017 02:51 PM
12-11-2017 04:18 PM - edited 12-11-2017 04:18 PM
Actually, I still have issues and these are:
1. Why are home routers, which are connected directly to PPPoE server, not getting DNS address? Please note that Windows clients that are connected directly to the same PPPoE server are able to get DNS address.
2. Is setting 'ppp ipcp dns x.x.x.x' on the PPPoE server's Interface Virtual-template1 okay to fix the DNS issue?
Hope that you can clarify this issue.
12-11-2017 04:21 PM
12-07-2017 04:58 PM
Hi
Without doing anything, you'll always see a /32 mask requested through ppp when using ip address negotiated on the client side.
To get a /24, you need to:
On Server side:
interface Virtual-Template1
ppp ipcp mask 255.255.255.0
On Client side:
ip dhcp pool LOCAL
import all
origin ipcp
!
interface Dialer1
ip address pool LOCAL
encapsulation ppp
dialer pool 1
ppp chap hostname MOMO
ppp chap password 0 123456789
ppp ipcp mask request --> Be able to get the right subnet mask
ppp ipcp route default --> Be able to get the default route
The DHCP pool configured locally isn't giving any IPs to the client but just here to negotiate the right parameters like mask
12-07-2017 05:04 PM
Hello Francesco,
A nice and insightful response!
One thing: Indeed, with ppp ipcp netmask, we can pass a different mask to the clients, but it won't make any difference as far as data flows are concerned. Because of PPPoE, communication between hosts associated to the same access concentrator (AC) will still need to go through the AC, regardless of the netmask, so changing it won't accomplish anything.
Do you personally see any value in sending a non-/32 netmask to PPPoE clients?
Best regards,
Peter
12-07-2017 05:12 PM
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