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30

The MTU is the Maximum IP packet size for a given link. Packets bigger than the MTU is fragmented at the point where the lower MTU is found and reassembled further down the chain. If no fragmentation is wanted, either you have to check the MTU at each hop or use a helper protocol for that (Path MTU Discovery). Note that IPv6 does NOT support packet ...


21

In addition. MSS value derives from the value MTU, if you have a 800-byte packet, it can also say that such a packet was originally 2260 bytes long, and he broke into 2 packet 1460 + 800 bytes, if we use MTU = 1500. You say is true, if you MSS = 800, the MTU should be at least 840. As PPPoE overhead is 8 bytes, and therefore MTU = 1492 bytes, and MSS = 1492-...


20

You might care to read RFC 1547 "Requirements for an Internet Standard Point-to-Point Protocol" which explains how the PPP was chosen. The thing I'd suggest you are missing is that interoperability is one of the principal driving forces in the internet protocols, and efficiency is much less important. You do the highly talented engineers who designed PPP a ...


12

Another reason may be that PPPoE is a tunnelling protocol which is useful for security and hiding an ISPs infrastructure. A tunnel is created between the end user CPE and ISP’s centralised BRAS. The network in-between is hidden from the user and the user cannot interact with other users directly over the ISP’s distribution network until it reaches the BRAS ...


11

So in the strictest sense, "IP over Ethernet" is exactly what it sounds like, it's the encapsulation of IP packets (datagrams, formally) in standard ethernet frames. For much of the networking universe this is just "normal" IP as so much of the transport has migrated to Ethernet nowadays. Somewhat more specifically speaking, IPoE is often used in ...


10

Is ADSL's UDP packet forwarding rate strictly linear to packet size? The answer is "no, because of the variable nature of ATM AAL5 padding used in ADSL lines". Since you aren't sure what encapsulation is used on the ADSL modem, I'll assume it's PPPoE, most providers use PPPoE for customer connections. I also assume that you've measured the full ATM ...


9

A few reasons. Firstly that is just the way it has always been and ISPs are loath to change a working setup. Secondly it's possible to create translators between different types of PPP. Just because what your router sees is PPPoE doesn't mean the path all the way back to your ISP is a simple ethernet network. You might have a setup that is PPPoE from your ...


9

IPoE is essentially DHCP-triggered subscriber interfaces. It has come about because most modern broadband access networks are able to deliver Ethernet from end-to-end (e.g.: xPON/FTTH). Users are "authenticated" through the use of DHCPv4/v6 Option-82 inserting their Circuit-ID into their initial DHCP Discovery - this identifies the physical location of the ...


7

NAT is applied to g0/0, not di0 where it is required. (there's no IP running on g0/0, so none of the IP configuration matters there.) int di0 ip nat outside ! no ip nat inside source list 1 interface GigabitEthernet0/1 overload ip nat inside source list 1 interface di0 overload The two route statements are not necessary. If you need something to trigger ...


7

Yes, the "E" in PPPoE stands for ethernet. The PPP stands for Point-to-Point Protocol. PPPoE and PPPoA are often used with DSL. PPP was the original protocol which was allowed by the DSL Forum. PPP provides more options and security for the ISP than does DHCP. For instance, DHCP offers no authentication, but that is built into of PPP. Juniper has a ...


7

The most and noticeable different is layer of tunneling. PPPOE is a Layer 2 (Data Link Layer) tunneling protocol while L2TP is a Layer 3 (Network Layer) tunneling protocol. This means that PPPOE can create a tunnel between devices in a broadcast domain (such as devices connect to the same switch) but L2TP can create a tunnel between two IP-based device ...


6

PPTP, PPPoE, and L2TP all provide OSI Layer 2 services. That is, the user of these protocols (usually, a network layer protocol suite) thinks it's running over a "normal" link layer. However, each of these protocols provides the link layer service by transporting packets over another service, rather than over the physical layer. PPTP provides PPP (link ...


6

*cough* interface Dialer0 ip nat outside


6

If I have a switch or laptop running a PPPOE server, could I go from ethernet-to-modem then connect the modem's WAN port to another modem's WAN port and have it connect via PPPOE? No. A DSL modem is the CPE part of a DSL link. You can't connect two CPEs, only CPE to COE, e.g. a DSLAM. DSLAMs usually require substantial infrastructure, so a lab environment ...


5

The NAT statement ip nat inside source list 1 interface GigabitEthernet0/1 overload is incorrect. You should specify the dialer0 interface instead. Here's a helpful link. http://www.cisco.com/en/US/docs/routers/access/800/850/software/configuration/guide/pppoenat.html#wp1235296


5

You are missing a critical NAT command. Try adding ip nat outside under the outbound dialer interface interface Dialer 0. With your current configuration you've identified the interface Gig 0/1 as the "Inside" interface, so the router knows when to apply NAT rules to the incoming traffic on that interface. However, since the Dialer 0 interface does not ...


5

I'd remove the Ericsson box. It isn't a BRAS. From your diagram it looks like you'd be using it as a aggregation switch and the Linux PPP Server would be your BRAS. Personally, for lab purposes I'd also remove the Linux PPP Server and hook the DSLAM up to a Cisco 3825 or 7200 configured as a BRAS. If you really want the Linux element set up a FreeRADIUS ...


5

The first diagram will not work, and in fact may result in damage to your router. The AUX port is a regular RS232 serial port, which is completely incompatible with ADSL. Don't do it. The second diagram should work, provided your D-Link modem can operate in bridged mode.


5

In this case, your router talks PPP to the provider directly. But first, the router puts this data into Ethernet frames which it transmits to the modem. (hence PPP-over-Ethernet) Since the modem is in bridge-mode, it won't interpret the frames, only encapsulate them itself in AAL (ATM Adaption Layer) or whatever in order to transmit over the public network ...


5

PPP doesn't use MAC addresses or ARP the way ethernet does, so no, there will not be ARP in PPP, but there may be ARP in the ethernet which carries the PPP frames. You will not see anything ethernet-related in the PPP. What you are looking at is the PPP, not the ethernet. ARP (Address Resolution Protocol) is used by some layer-2 protocols, e.g. ethernet, to ...


4

Testing that kind of features using GNS3 is simply waste of time. You're emulating at run-time complex software, and on top of that, you're adding complex features. There's no sense in 'trying' 7200 as 7200 are long EoS: http://www.cisco.com/c/en/us/products/collateral/routers/7200-series-routers/end_of_life_c51-681414.html Download CSR 1000v and test in ...


4

Adding to the other answers... the thing you lack now is an access-list to limit NAT to your inside addresses... if you apply this configuration, I think this should get you going as long as there aren't other subnets routed by this router. ! interface GigabitEthernet0/1 ip address 192.168.2.1 255.255.255.0 ip nat inside interface Dialer0 ip nat ...


4

For your home router to establish a WAN connection to your ISP, a few things specific to PPP must happen first. You may also have to do some research on LCP and NCP. Check this link below, it may have the answer you are looking for (see the excerpt on PPPoE below): https://infoproducts.alcatel-lucent.com/html/0_add-h-f/93-0098-09-01/...


4

I think what you want to set is the interface MTU not the ip MTU. Just use this command and you will be good to go: mtu 1492 But the ppp mtu adaptive is usually the way to go


4

Except the 1750 only has one fastethernet port. A WIC-1ENET is 10m, WIC-4ESW a 4 port switch... but they both live on the WIC bus that'll top out about 6-8m. Depending on your DSL speed, this may not be a problem. I use a WIC-1ADSL (and WIC-4ESW) in a 1720, but the DSL line is 6m anyway. (and neither the 1720 nor 1750 support dot1q; that's a feature of ...


4

According to Cisco, you cannot use DHCP with PPPoE, : PPPoE is not supported in conjunction with DHCP because with PPPoE the IP address is assigned by PPP. Juniper has a whitepaper about Understanding PPPoE and DHCP: The DSL Forum now also allows using IP over Ethernet (IPoE), which is based on DHCP. However, PPP remains the more mature and robust ...


4

Can you explain what happens to the frames tagged 100 as they go through (or try to go through) this Gi0/0/0.1 sub-interface? First, let's be a little more clear about your configuration for other readers. More than likely, you also have an interface in the router configured like this: interface Dialer1 mtu 1492 ip address negotiated ip nat outside ip ...


3

Have a look @ http://blog.ipspace.net/2011/09/ipv6-mplsvpn-6vpe-with-pppoe-and-radius.html Is this what you are trying to achieve? They confirm that: Cisco-AVPair += "ip:vrf-id=vrf-name", Cisco-AVPair += "ip:ip-unnumbered=Loopback301" would only work with IPv4. In order to make IPv6 work, you would need the following: cisco-avpair += "lcp:interface-...


3

No. ADSL uses different upstream and downstream frequency ranges. As such, a modem is designed to transmit only in a narrow, low frequency range for which is has no receive capability. (The much older, SDSL, does work head-to-head.)


3

Note that layer three and above protocols can be encapsulated inside the protocols you mention but not layer two (or below). One way to look at it is that you build a protocol stack from the bottom up. So first we put down layers 1, 2, and 3. Then for layer 4 we put PPTP (for example) and that starts a NEW layer 2 on top of (inside of) the "real" layers 1, 2,...


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