Update custom-docker0.md (corrections)

Corrected outdated internal link (regarding ```ip_forward``` system setting) . Corrected missing newline before bulleted list (for options configurable at server startup).

Signed-off-by: Devvyn Murphy <devvyn@devvyn.com>

docs/userguide/networking/default_network/custom-docker0.md

@@ -17,6 +17,7 @@ The information in this section explains how to customize the Docker default bri
 By default, the Docker server creates and configures the host system's `docker0` interface as an _Ethernet bridge_ inside the Linux kernel that can pass packets back and forth between other physical or virtual network interfaces so that they behave as a single Ethernet network.
 
 Docker configures `docker0` with an IP address, netmask and IP allocation range. The host machine can both receive and send packets to containers connected to the bridge, and gives it an MTU -- the _maximum transmission unit_ or largest packet length that the interface will allow -- of 1,500 bytes. These options are configurable at server startup:
+
 - `--bip=CIDR` -- supply a specific IP address and netmask for the `docker0` bridge, using standard CIDR notation like `192.168.1.5/24`.
 
 - `--fixed-cidr=CIDR` -- restrict the IP range from the `docker0` subnet, using the standard CIDR notation like `172.167.1.0/28`. This range must be an IPv4 range for fixed IPs (ex: 10.20.0.0/16) and must be a subset of the bridge IP range (`docker0` or set using `--bridge`). For example with `--fixed-cidr=192.168.1.0/25`, IPs for your containers will be chosen from the first half of `192.168.1.0/24` subnet.
@@ -58,4 +59,4 @@ default via 172.17.42.1 dev eth0
 $$ exit
 ```
 
-Remember that the Docker host will not be willing to forward container packets out on to the Internet unless its `ip_forward` system setting is `1` -- see the section above on [Communication between containers](#between-containers) for details.
+Remember that the Docker host will not be willing to forward container packets out on to the Internet unless its `ip_forward` system setting is `1` -- see the section on [Communicating to the outside world](container-communication.md#communicating-to-the-outside-world) for details.