until now there is no solution for this issue. I reported it to cisco and they will add it in the next Firmware.
I got this answer on August 31th:
We have submitted your request for the "DE-WAP321-feature request - more characters for the captive portal" to be added to the firmware. This might take months to come up with a firmware that will have the feature added in. Please check future firmware for this Bug number "CSCub92801" . We will place on the release note of future firmware upgrades to the DE-WAP321. At this point we will be close this case
It may be too late, but with the new version22.214.171.124 software you can create a cluster of up to 8 WAP321's in order to share one configuration. The feature is called Single Point. Here is a paper on the feature
Special thanks to Alex McDonald for sharing his favorite tip:My favorite
tip is the ‘write default’ command on autonomous wireless access points,
it simplifies manual conversion of a WAP with a static ip address to a
LAP with a DHCP address.This saved a l...
With the latest release of firmware for the WAP 561, 551, 371, 351 a new
feature was added that would allow customers to upgrade the firmware for
their clustered access points from the main access point.The basic steps
to accomplish this is:1) Download th...