A traditional Irish quatrain of 7-syllable lines ('old-school'), or 8-6-8-6, ending in 2-syllable words all linked by consonance (in its old meaning, 'having the same vowels'), with at least two cross-rimes in each couplet (can be consonance in first but should be rime in second)
and alliteration in every line, which in the second couplet must be between the last two stressed words in each line, and with the dunedh, of course (ending in the same word, phrase, or line it began with).
As with the other Irish forms, a template can show you the syllable count and a bit more, but cannot be definitive as so much variation
is possible while meeting the formal requirements.
In the example below some words not hi-lited could have been as serving one or more rules.