Question about IPoE shared mode vs PPPoE

IPoE related questions
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wobo
Posts: 2
Joined: 26 Jan 2018, 10:41

Question about IPoE shared mode vs PPPoE

Post by wobo » 26 Jan 2018, 12:49

Hello.

I have couple questions about IPOE shared mode from someone who has been using PPPoE only.

PPPOE:
On two PPPoE servers I have 3 interfaces: (one WAN (e.g eth0), one LAN(many vlans terminated, eg. eth1.100, eth1.101, eth1.102, etc...), one loopback (dummy0) interface).
Accel-ppp is set to listen on the LAN interface(s). PPPoE sessions are established to the server's loopback interface as the tunnel endpoint. (Loopback address/32 <-> Client address/32).
This allows:
+ easy load balancing (PADO delay, multiple servers listening on the same vlan)
+ quick failure recovery (Clients reconnecting quickly to other servers when LCP echos timeout)
+ no ip addresses wasted at all (private or public it doesn't matter) all addresses are a /32 and can easily be redistributed to ospf or bgp as /32 subnets

IPOE (L2 mode, shared=1):
Questions:
- Can I run IPOE shared mode in the same vlans on two or more servers?
- Can I use IPOE DHCP Offer delay in shared mode to load balance?
- For failure detection is it considered OK to run a low dhcp lease time (e.g 300 seconds)?
- Is disabling kernel proxy arp mandatory even if accel-ppp's ipoe settings contains: proxy-arp=0?
- How do I specify the gateways to clients? Do I need to have a different gateway on each server or it will work with the same one? For example:

Client receives Framed-Ip-Address=1.2.3.4 from Radius:

Is this correct?
#server1:
[ipoe]
ifcfg=1
gw-ip-address=1.2.3.1/24
#server 2:
[ipoe]
ifcfg=1
gw-ip-address=1.2.3.1/24

Or would I need to have a separate gateway in each server? For example:
server1: [ipoe] gw-ip-address=1.2.3.1/24
server2: [ipoe] gw-ip-address=1.2.3.254/24

- It is not necessary to manually add a gateway address at all, accel-ppp configures it automatically if ifcfg=1 is present. Is this correct?
- Can PPPOE's flexibility regarding /32 client addresses be replicated in IPOE's shared mode? (The less wasted addresses the better)

Thank you kindly.

Dmitry
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Posts: 949
Joined: 09 Oct 2014, 10:06

Re: Question about IPoE shared mode vs PPPoE

Post by Dmitry » 26 Jan 2018, 17:10

- Can I run IPOE shared mode in the same vlans on two or more servers?
yes
- Can I use IPOE DHCP Offer delay in shared mode to load balance?
yes
- For failure detection is it considered OK to run a low dhcp lease time (e.g 300 seconds)?
yes
- Is disabling kernel proxy arp mandatory even if accel-ppp's ipoe settings contains: proxy-arp=0?
yes, because kernel proxy-arp affects gratuitous arp, accel-ppp's proxy-arp is replacement
- How do I specify the gateways to clients? Do I need to have a different gateway on each server or it will work with the same one?
use gw-ip-address options in [ipoe] section, you must to use different gateway addresses on different servers
Is this correct?
#server1:
[ipoe]
ifcfg=1
gw-ip-address=1.2.3.1/24
#server 2:
[ipoe]
ifcfg=1
gw-ip-address=1.2.3.1/24
no
Or would I need to have a separate gateway in each server? For example:
server1: [ipoe] gw-ip-address=1.2.3.1/24
server2: [ipoe] gw-ip-address=1.2.3.254/24
yes

wobo
Posts: 2
Joined: 26 Jan 2018, 10:41

Re: Question about IPoE shared mode vs PPPoE

Post by wobo » 26 Jan 2018, 17:18

Thank you. This has cleared some doubts I had. So basically the only tradeoff is that it is necessary to sacrifice some ip addresses for the gateways.

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