For SLE 11 SP3 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:OpenVAS:UNSTABLE:v6/SLE_11_SP3/security:OpenVAS:UNSTABLE:v6.repo
zypper refresh
zypper install libgnutls-extra26
For SLE 11 SP2 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:OpenVAS:UNSTABLE:v6/SLE_11_SP2/security:OpenVAS:UNSTABLE:v6.repo
zypper refresh
zypper install libgnutls-extra26
For SLE 11 SP1 run the following as root:
zypper addrepo https://download.opensuse.org/repositories/security:OpenVAS:UNSTABLE:v6/SLE_11_SP1/security:OpenVAS:UNSTABLE:v6.repo
zypper refresh
zypper install libgnutls-extra26