Q. I was attending a neighbourhood Simchas Bais Hashoeva and a neighbor walked in in the sukkah with his friendly, well behaved but rather large family dog, that did not seem to bother anyone and trilled the children. Is it correct to bring in a dog to a sukkah?

A. On question 861 on this forum, in regards to a seeing eye dog to go up the bimah when the blind owner is given an aliyah, we mentioned the following; Igrois Moshe (O.H. 1: 45) permits the attendance of a seeing eye dog to shul when needed. Sha’are Halacha Uminchag (p.204) further asserts that from the fact that the Talmud (Yuma 21b) describes the heavenly fire resting in the altar as taking the form of a dog, it would seem that there is no unsuitable connotation in a dog’s presence, other Poskim disagree.
However. Chelkas Ya’akov (O.H. 34) differs with the Igrois Moshe leniency, since the presence of the dog may cause levity and frivolous distractions especially among the youngsters. He also argues about safety, two concerns that may not seem valid today in many shuln. Yalkut Yosef (150: 25) quoting Horav Ovadia Yosef zt”l is also stringent since the dog could easily be placed outside, and the blind be helped by the other attendants to the shul. (See Hatefila Vehilchateha p. 170)
Horav Shlomo Miller’s Shlit”a opinion is that if it is possible for someone to help the blind man up the bimah it is preferable. The most important issue is to avoid this becoming a source of machlokes and conflict.
In general, we find conflicting attitudes in regards to dogs in our tradition. Megaleh Amukos points out that the gimatria of “kelev ra’a” or bad dog is 322 same as Baal Tzefon, while the numerical value of “kelev tov” or good dog equals Eliahu. This alludes to the aphorism (Bava Kama 60b) if the dogs yowl, the Angel of Death is entering the city, if they revel, Eliahu Hanovi is coming. Rosh Simchosi (Vaero p. 462) quotes Mekubalim that maintain it is the “k’lavim dik’dusha” who sing shira and on whom the pasuk (Shemos 11: 7) says “And to the Bnei Yisroel no dog will.” Yet, he also quotes the saying that the one who speaks lashon hora’a will reincarnate in a dog (see P’sachim 116a.) We also find that the mechir kelev or monies obtained from a dog’s sale cannot be used for the purchase of a korban and are comparable to the wages of a harlot. The dog was punished because he was in the group of the three who continued cohabitation on Noach’s Teva (Sanhedrin 108b.) Then again Divrei Yosher (Sanhedrin p. 101} quotes the saying that “kelev” stands for “kulo lev,” he is all heart and totally bonds with his master to become man’s best friend. There is also an old Yidish adage that if a Yid owns a dog, either the dog is not a dog or the Yid is not a Yid.
Horav Shlomo Miller’s Shlit”a opinion is that in principle if one owns a dog that freely and constantly roams around his house, he would be allowed to be in the suka too, as this complies with “teshvu ke’in toduru,” dwell in you suka, as you would in your house. However, it is commendable to create and maintain a higher spirit of kedusha in the suka than in the house. On entering someone else suka with a dog, he should ask permission first. As in previous question; the most important issue is to avoid this becoming a source of machlokes and conflict or for the ba’al habbais to publicly embarrass his guest.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a