User`s guide

IP Routing
6-5
8000-A2-GB21-10
June 1997
Source-Based Routing
In addition to destination-based routing, the HotWire DSLAM system also
supports source-based routing. Source-based routing is a security feature for
preventing ES-to-ES routing when they are attached to LANs on different RTUs
that are attached to the same DSL card. That is, sourced-based routing can
ensure that all upstream traffic within a customer’s domain is sent to the ISP.
Without Source-Based Routing
The following illustration shows, for example, that with destination routing ES1
can send packets to ES2 based on the static route table. That is, when ES1
sends a packet to ES2, the destination route is 159.1.3.4 and the next hop
address for this destination is 135.1.3.4 (RTU 2).
97-15472-0
1
Router
155.1.3.1
DSL Card
s1c
RTU 1
135.1.3.3
155.1.3.4
ES1
s1d
RTU 2
135.1.3.4
155.1.3.5
ES2
Packet Flow
Host/Net/Subnet
1) 155.1.3.4
2) 155.1.3.5
3) 0.0.0.0
Subnet Mask
255.255.255.255
255.255.255.255
0.0.0.0
Next-Hop Address
135.1.3.3
135.1.3.4
155.1.3.1
S/D (Source/Destination)
dst (destination)
dst (destination)
dst (destination)
DSL Routing Table
With Source-Based Routing
With source-based routing, the source address of upstream packets sent from an
ES are compared to the source address listed in the static route table. If a match
is found, the packet is sent to the next-hop address specified for that source
address.
The following illustration shows the packet flow when ES1 sends to ES2, and
when source-based routes are defined for ES1 and ES2 (indicated by the S/D
flag).